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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v9 11/13] arm/mem_access: Add long-descriptor based gpt
This commit adds functionality to walk the guest's page tables using the
long-descriptor translation table format for both ARMv7 and ARMv8.
Similar to the hardware architecture, the implementation supports
different page granularities (4K, 16K, and 64K). The implementation is
based on ARM DDI 0487B.a J1-5922, J1-5999, and ARM DDI 0406C.b B3-1510.
Note that the current implementation lacks support for Large VA/PA on
ARMv8.2 architectures (LVA/LPA, 52-bit virtual and physical address
sizes). The associated location in the code is marked appropriately.
Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
v2: Use TCR_SZ_MASK instead of TTBCR_SZ_MASK for ARM 32-bit guests using
the long-descriptor translation table format.
Cosmetic fixes.
v3: Move the implementation to ./xen/arch/arm/guest_copy.c.
Remove the array strides and declare the array grainsizes as static
const instead of just const to reduce the function stack overhead.
Move parts of the funtion guest_walk_ld into the static functions
get_ttbr_and_gran_64bit and get_top_bit to reduce complexity.
Use the macro BIT(x) instead of (1UL << x).
Add more comments && Cosmetic fixes.
v4: Move functionality responsible for determining the configured IPA
output-size into a separate function get_ipa_output_size. In this
function, we remove the previously used switch statement, which was
responsible for distinguishing between different IPA output-sizes.
Instead, we retrieve the information from the introduced ipa_sizes
array.
Remove the defines GRANULE_SIZE_INDEX_* and TTBR0_VALID from
guest_walk.h. Instead, introduce the enums granule_size_index
active_ttbr directly inside of guest_walk.c so that the associated
fields don't get exported.
Adapt the function to the new parameter of type "struct vcpu *".
Remove support for 52bit IPA output-sizes entirely from this commit.
Use lpae_* helpers instead of p2m_* helpers.
Cosmetic fixes & Additional comments.
v5: Make use of the function vgic_access_guest_memory to read page table
entries in guest memory.
Invert the indeces of the arrays "offsets" and "masks" and simplify
readability by using an appropriate macro for the entries.
Remove remaining CONFIG_ARM_64 #ifdefs.
Remove the use of the macros BITS_PER_WORD and BITS_PER_DOUBLE_WORD.
Use GENMASK_ULL instead of manually creating complex masks to ease
readability.
Also, create a macro CHECK_BASE_SIZE which simply reduces the code
size and simplifies readability.
Make use of the newly introduced lpae_page macro in the if-statement
to test for invalid/reserved mappings in the L3 PTE.
Cosmetic fixes and additional comments.
v6: Convert the macro CHECK_BASE_SIZE into a helper function
check_base_size. The use of the old CHECK_BASE_SIZE was confusing as
it affected the control-flow through a return as part of the macro.
Return the value -EFAULT instead of -EINVAL if access to the guest's
memory fails.
Simplify the check in the end of the table walk that ensures that
the found PTE is a page or a superpage. The new implementation
checks if the pte maps a valid page or a superpage and returns an
-EFAULT only if both conditions are not true.
Adjust the type of the array offsets to paddr_t instead of vaddr_t
to allow working with the changed *_table_offset_* helpers, which
return offsets of type paddr_t.
Make use of renamed function access_guest_memory_by_ipa instead of
vgic_access_guest_memory.
v7: Change the return type of check_base_size to bool as it returns only
two possible values and the caller is interested only whether the call
has succeeded or not.
Use a mask for the computation of the IPA, as the lower values of
the PTE's base address do not need to be zeroed out.
Cosmetic fixes in comments.
v8: By calling access_guest_memory_by_ipa in guest_walk_(ld|sd), we rely
on the p2m->lock (rw_lock) to be recursive. To avoid bugs in the
future implementation, we add a comment in struct p2m_domain to
address this case. Thus, we make the future implementation aware of
the nested use of the lock.
v9: Remove second "to" in a comment.
Add Acked-by Julien Grall.
---
xen/arch/arm/guest_walk.c | 398 +++++++++++++++++++++++++++++++++++++++++++++-
xen/include/asm-arm/p2m.h | 8 +-
2 files changed, 403 insertions(+), 3 deletions(-)
diff --git a/xen/arch/arm/guest_walk.c b/xen/arch/arm/guest_walk.c
index 78badc2949..d0d45ad659 100644
--- a/xen/arch/arm/guest_walk.c
+++ b/xen/arch/arm/guest_walk.c
@@ -15,7 +15,10 @@
* this program; If not, see <http://www.gnu.org/licenses/>.
*/
+#include <xen/domain_page.h>
#include <xen/sched.h>
+#include <asm/guest_access.h>
+#include <asm/guest_walk.h>
/*
* The function guest_walk_sd translates a given GVA into an IPA using the
@@ -33,6 +36,174 @@ static int guest_walk_sd(const struct vcpu *v,
}
/*
+ * Get the IPA output_size (configured in TCR_EL1) that shall be used for the
+ * long-descriptor based translation table walk.
+ */
+static int get_ipa_output_size(struct domain *d, register_t tcr,
+ unsigned int *output_size)
+{
+ unsigned int ips;
+
+ static const unsigned int ipa_sizes[7] = {
+ TCR_EL1_IPS_32_BIT_VAL,
+ TCR_EL1_IPS_36_BIT_VAL,
+ TCR_EL1_IPS_40_BIT_VAL,
+ TCR_EL1_IPS_42_BIT_VAL,
+ TCR_EL1_IPS_44_BIT_VAL,
+ TCR_EL1_IPS_48_BIT_VAL,
+ TCR_EL1_IPS_52_BIT_VAL
+ };
+
+ if ( is_64bit_domain(d) )
+ {
+ /* Get the intermediate physical address size. */
+ ips = (tcr & TCR_EL1_IPS_MASK) >> TCR_EL1_IPS_SHIFT;
+
+ /*
+ * Return an error on reserved IPA output-sizes and if the IPA
+ * output-size is 52bit.
+ *
+ * XXX: 52 bit output-size is not supported yet.
+ */
+ if ( ips > TCR_EL1_IPS_48_BIT )
+ return -EFAULT;
+
+ *output_size = ipa_sizes[ips];
+ }
+ else
+ *output_size = TCR_EL1_IPS_40_BIT_VAL;
+
+ return 0;
+}
+
+/* Normalized page granule size indices. */
+enum granule_size_index {
+ GRANULE_SIZE_INDEX_4K,
+ GRANULE_SIZE_INDEX_16K,
+ GRANULE_SIZE_INDEX_64K
+};
+
+/* Represent whether TTBR0 or TTBR1 is active. */
+enum active_ttbr {
+ TTBR0_ACTIVE,
+ TTBR1_ACTIVE
+};
+
+/*
+ * Select the TTBR(0|1)_EL1 that will be used for address translation using the
+ * long-descriptor translation table format and return the page granularity
+ * that is used by the selected TTBR. Please note that the TCR.TG0 and TCR.TG1
+ * encodings differ.
+ */
+static bool get_ttbr_and_gran_64bit(uint64_t *ttbr, unsigned int *gran,
+ register_t tcr, enum active_ttbr ttbrx)
+{
+ bool disabled;
+
+ if ( ttbrx == TTBR0_ACTIVE )
+ {
+ /* Normalize granule size. */
+ switch ( tcr & TCR_TG0_MASK )
+ {
+ case TCR_TG0_16K:
+ *gran = GRANULE_SIZE_INDEX_16K;
+ break;
+ case TCR_TG0_64K:
+ *gran = GRANULE_SIZE_INDEX_64K;
+ break;
+ default:
+ /*
+ * According to ARM DDI 0487B.a D7-2487, if the TCR_EL1.TG0 value
+ * is programmed to either a reserved value, or a size that has not
+ * been implemented, then the hardware will treat the field as if
+ * it has been programmed to an IMPLEMENTATION DEFINED choice.
+ *
+ * This implementation strongly follows the pseudo-code
+ * implementation from ARM DDI 0487B.a J1-5924 which suggests to
+ * fall back to 4K by default.
+ */
+ *gran = GRANULE_SIZE_INDEX_4K;
+ }
+
+ /* Use TTBR0 for GVA to IPA translation. */
+ *ttbr = READ_SYSREG64(TTBR0_EL1);
+
+ /* If TCR.EPD0 is set, translations using TTBR0 are disabled. */
+ disabled = tcr & TCR_EPD0;
+ }
+ else
+ {
+ /* Normalize granule size. */
+ switch ( tcr & TCR_EL1_TG1_MASK )
+ {
+ case TCR_EL1_TG1_16K:
+ *gran = GRANULE_SIZE_INDEX_16K;
+ break;
+ case TCR_EL1_TG1_64K:
+ *gran = GRANULE_SIZE_INDEX_64K;
+ break;
+ default:
+ /*
+ * According to ARM DDI 0487B.a D7-2486, if the TCR_EL1.TG1 value
+ * is programmed to either a reserved value, or a size that has not
+ * been implemented, then the hardware will treat the field as if
+ * it has been programmed to an IMPLEMENTATION DEFINED choice.
+ *
+ * This implementation strongly follows the pseudo-code
+ * implementation from ARM DDI 0487B.a J1-5924 which suggests to
+ * fall back to 4K by default.
+ */
+ *gran = GRANULE_SIZE_INDEX_4K;
+ }
+
+ /* Use TTBR1 for GVA to IPA translation. */
+ *ttbr = READ_SYSREG64(TTBR1_EL1);
+
+ /* If TCR.EPD1 is set, translations using TTBR1 are disabled. */
+ disabled = tcr & TCR_EPD1;
+ }
+
+ return disabled;
+}
+
+/*
+ * Get the MSB number of the GVA, according to "AddrTop" pseudocode
+ * implementation in ARM DDI 0487B.a J1-6066.
+ */
+static unsigned int get_top_bit(struct domain *d, vaddr_t gva, register_t tcr)
+{
+ unsigned int topbit;
+
+ /*
+ * If EL1 is using AArch64 then addresses from EL0 using AArch32 are
+ * zero-extended to 64 bits (ARM DDI 0487B.a J1-6066).
+ */
+ if ( is_32bit_domain(d) )
+ topbit = 31;
+ else if ( is_64bit_domain(d) )
+ {
+ if ( ((gva & BIT_ULL(55)) && (tcr & TCR_EL1_TBI1)) ||
+ (!(gva & BIT_ULL(55)) && (tcr & TCR_EL1_TBI0)) )
+ topbit = 55;
+ else
+ topbit = 63;
+ }
+
+ return topbit;
+}
+
+/* Make sure the base address does not exceed its configured size. */
+static bool check_base_size(unsigned int output_size, uint64_t base)
+{
+ paddr_t mask = GENMASK_ULL((TCR_EL1_IPS_48_BIT_VAL - 1), output_size);
+
+ if ( (output_size < TCR_EL1_IPS_48_BIT_VAL) && (base & mask) )
+ return false;
+
+ return true;
+}
+
+/*
* The function guest_walk_ld translates a given GVA into an IPA using the
* long-descriptor translation table format in software. This function assumes
* that the domain is running on the currently active vCPU. To walk the guest's
@@ -43,8 +214,231 @@ static int guest_walk_ld(const struct vcpu *v,
vaddr_t gva, paddr_t *ipa,
unsigned int *perms)
{
- /* Not implemented yet. */
- return -EFAULT;
+ int ret;
+ bool disabled = true;
+ bool ro_table = false, xn_table = false;
+ unsigned int t0_sz, t1_sz;
+ unsigned int level, gran;
+ unsigned int topbit = 0, input_size = 0, output_size;
+ uint64_t ttbr = 0;
+ paddr_t mask, paddr;
+ lpae_t pte;
+ register_t tcr = READ_SYSREG(TCR_EL1);
+ struct domain *d = v->domain;
+
+#define OFFSETS(gva, gran) \
+{ \
+ zeroeth_table_offset_##gran(gva), \
+ first_table_offset_##gran(gva), \
+ second_table_offset_##gran(gva), \
+ third_table_offset_##gran(gva) \
+}
+
+ const paddr_t offsets[3][4] = {
+ OFFSETS(gva, 4K),
+ OFFSETS(gva, 16K),
+ OFFSETS(gva, 64K)
+ };
+
+#undef OFFSETS
+
+#define MASKS(gran) \
+{ \
+ zeroeth_size(gran) - 1, \
+ first_size(gran) - 1, \
+ second_size(gran) - 1, \
+ third_size(gran) - 1 \
+}
+
+ static const paddr_t masks[3][4] = {
+ MASKS(4K),
+ MASKS(16K),
+ MASKS(64K)
+ };
+
+#undef MASKS
+
+ static const unsigned int grainsizes[3] = {
+ PAGE_SHIFT_4K,
+ PAGE_SHIFT_16K,
+ PAGE_SHIFT_64K
+ };
+
+ t0_sz = (tcr >> TCR_T0SZ_SHIFT) & TCR_SZ_MASK;
+ t1_sz = (tcr >> TCR_T1SZ_SHIFT) & TCR_SZ_MASK;
+
+ /* Get the MSB number of the GVA. */
+ topbit = get_top_bit(d, gva, tcr);
+
+ if ( is_64bit_domain(d) )
+ {
+ /* Select the TTBR(0|1)_EL1 that will be used for address translation.
*/
+
+ if ( (gva & BIT_ULL(topbit)) == 0 )
+ {
+ input_size = 64 - t0_sz;
+
+ /* Get TTBR0 and configured page granularity. */
+ disabled = get_ttbr_and_gran_64bit(&ttbr, &gran, tcr,
TTBR0_ACTIVE);
+ }
+ else
+ {
+ input_size = 64 - t1_sz;
+
+ /* Get TTBR1 and configured page granularity. */
+ disabled = get_ttbr_and_gran_64bit(&ttbr, &gran, tcr,
TTBR1_ACTIVE);
+ }
+
+ /*
+ * The current implementation supports intermediate physical address
+ * sizes (IPS) up to 48 bit.
+ *
+ * XXX: Determine whether the IPS_MAX_VAL is 48 or 52 in software.
+ */
+ if ( (input_size > TCR_EL1_IPS_48_BIT_VAL) ||
+ (input_size < TCR_EL1_IPS_MIN_VAL) )
+ return -EFAULT;
+ }
+ else
+ {
+ /* Granule size of AArch32 architectures is always 4K. */
+ gran = GRANULE_SIZE_INDEX_4K;
+
+ /* Select the TTBR(0|1)_EL1 that will be used for address translation.
*/
+
+ /*
+ * Check if the bits <31:32-t0_sz> of the GVA are set to 0 (DDI 0487B.a
+ * J1-5999). If so, TTBR0 shall be used for address translation.
+ */
+ mask = GENMASK_ULL(31, (32 - t0_sz));
+
+ if ( t0_sz == 0 || !(gva & mask) )
+ {
+ input_size = 32 - t0_sz;
+
+ /* Use TTBR0 for GVA to IPA translation. */
+ ttbr = READ_SYSREG64(TTBR0_EL1);
+
+ /* If TCR.EPD0 is set, translations using TTBR0 are disabled. */
+ disabled = tcr & TCR_EPD0;
+ }
+
+ /*
+ * Check if the bits <31:32-t1_sz> of the GVA are set to 1 (DDI 0487B.a
+ * J1-6000). If so, TTBR1 shall be used for address translation.
+ */
+ mask = GENMASK_ULL(31, (32 - t1_sz));
+
+ if ( ((t1_sz == 0) && !ttbr) || (t1_sz && (gva & mask) == mask) )
+ {
+ input_size = 32 - t1_sz;
+
+ /* Use TTBR1 for GVA to IPA translation. */
+ ttbr = READ_SYSREG64(TTBR1_EL1);
+
+ /* If TCR.EPD1 is set, translations using TTBR1 are disabled. */
+ disabled = tcr & TCR_EPD1;
+ }
+ }
+
+ if ( disabled )
+ return -EFAULT;
+
+ /*
+ * The starting level is the number of strides (grainsizes[gran] - 3)
+ * needed to consume the input address (ARM DDI 0487B.a J1-5924).
+ */
+ level = 4 - DIV_ROUND_UP((input_size - grainsizes[gran]),
(grainsizes[gran] - 3));
+
+ /* Get the IPA output_size. */
+ ret = get_ipa_output_size(d, tcr, &output_size);
+ if ( ret )
+ return -EFAULT;
+
+ /* Make sure the base address does not exceed its configured size. */
+ ret = check_base_size(output_size, ttbr);
+ if ( !ret )
+ return -EFAULT;
+
+ /*
+ * Compute the base address of the first level translation table that is
+ * given by TTBRx_EL1 (ARM DDI 0487B.a D4-2024 and J1-5926).
+ */
+ mask = GENMASK_ULL(47, grainsizes[gran]);
+ paddr = (ttbr & mask);
+
+ for ( ; ; level++ )
+ {
+ /*
+ * Add offset given by the GVA to the translation table base address.
+ * Shift the offset by 3 as it is 8-byte aligned.
+ */
+ paddr |= offsets[gran][level] << 3;
+
+ /* Access the guest's memory to read only one PTE. */
+ ret = access_guest_memory_by_ipa(d, paddr, &pte, sizeof(lpae_t),
false);
+ if ( ret )
+ return -EFAULT;
+
+ /* Make sure the base address does not exceed its configured size. */
+ ret = check_base_size(output_size, pfn_to_paddr(pte.walk.base));
+ if ( !ret )
+ return -EFAULT;
+
+ /*
+ * If page granularity is 64K, make sure the address is aligned
+ * appropriately.
+ */
+ if ( (output_size < TCR_EL1_IPS_52_BIT_VAL) &&
+ (gran == GRANULE_SIZE_INDEX_64K) &&
+ (pte.walk.base & 0xf) )
+ return -EFAULT;
+
+ /*
+ * Break if one of the following conditions is true:
+ *
+ * - We have found the PTE holding the IPA (level == 3).
+ * - The PTE is not valid.
+ * - If (level < 3) and the PTE is valid, we found a block descriptor.
+ */
+ if ( level == 3 || !lpae_valid(pte) || lpae_is_superpage(pte, level) )
+ break;
+
+ /*
+ * Temporarily store permissions of the table descriptor as they are
+ * inherited by page table attributes (ARM DDI 0487B.a J1-5928).
+ */
+ xn_table |= pte.pt.xnt; /* Execute-Never */
+ ro_table |= pte.pt.apt & BIT(1); /* Read-Only */
+
+ /* Compute the base address of the next level translation table. */
+ mask = GENMASK_ULL(47, grainsizes[gran]);
+ paddr = pfn_to_paddr(pte.walk.base) & mask;
+ }
+
+ /*
+ * According to ARM DDI 0487B.a J1-5927, we return an error if the found
+ * PTE is invalid or holds a reserved entry (PTE<1:0> == x0)) or if the PTE
+ * maps a memory block at level 3 (PTE<1:0> == 01).
+ */
+ if ( !lpae_is_page(pte, level) && !lpae_is_superpage(pte, level) )
+ return -EFAULT;
+
+ /* Make sure that the lower bits of the PTE's base address are zero. */
+ mask = GENMASK_ULL(47, grainsizes[gran]);
+ *ipa = (pfn_to_paddr(pte.walk.base) & mask) | (gva & masks[gran][level]);
+
+ /*
+ * Set permissions so that the caller can check the flags by herself. Note
+ * that stage 1 translations also inherit attributes from the tables
+ * (ARM DDI 0487B.a J1-5928).
+ */
+ if ( !pte.pt.ro && !ro_table )
+ *perms |= GV2M_WRITE;
+ if ( !pte.pt.xn && !xn_table )
+ *perms |= GV2M_EXEC;
+
+ return 0;
}
int guest_walk_tables(const struct vcpu *v, vaddr_t gva,
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index 1269052e9f..aa0d60ae3a 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -21,7 +21,13 @@ extern void memory_type_changed(struct domain *);
/* Per-p2m-table state */
struct p2m_domain {
- /* Lock that protects updates to the p2m */
+ /*
+ * Lock that protects updates to the p2m.
+ *
+ * Please note that we use this lock in a nested way by calling
+ * access_guest_memory_by_ipa in guest_walk_(sd|ld). This must be
+ * considered in the future implementation.
+ */
rwlock_t lock;
/* Pages used to construct the p2m */
--
2.13.3
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