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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 4/6] tools/libxc: Remove xsave calculations from libxc
libxc performs a lot of calculations for the xstate leaf when generating a
guests cpuid policy. To correctly construct a policy for an HVM guest, this
logic depends on native cpuid leaking through from real hardware.
In particular, the logic is potentially wrong for an HVM-based toolstack
domain (e.g. PVH dom0), and definitely wrong if cpuid faulting is applied to a
PV domain.
Xen now performs all the necessary calculations, using native values. The
only piece of information the toolstack need worry about is single xstate
feature leaf.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
---
tools/libxc/xc_cpuid_x86.c | 143 +++++----------------------------------------
1 file changed, 15 insertions(+), 128 deletions(-)
diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index b32001b3..96d6025 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -400,125 +400,6 @@ static void intel_xc_cpuid_policy(xc_interface *xch,
}
}
-/* XSTATE bits in XCR0. */
-#define X86_XCR0_X87 (1ULL << 0)
-#define X86_XCR0_SSE (1ULL << 1)
-#define X86_XCR0_AVX (1ULL << 2)
-#define X86_XCR0_BNDREG (1ULL << 3)
-#define X86_XCR0_BNDCSR (1ULL << 4)
-#define X86_XCR0_OPMASK (1ULL << 5)
-#define X86_XCR0_ZMM (1ULL << 6)
-#define X86_XCR0_HI_ZMM (1ULL << 7)
-#define X86_XCR0_PKRU (1ULL << 9)
-#define X86_XCR0_LWP (1ULL << 62)
-
-#define X86_XSS_MASK (0) /* No XSS states supported yet. */
-
-/* Per-component subleaf flags. */
-#define XSTATE_XSS (1ULL << 0)
-#define XSTATE_ALIGN64 (1ULL << 1)
-
-/* Configure extended state enumeration leaves (0x0000000D for xsave) */
-static void xc_cpuid_config_xsave(xc_interface *xch,
- const struct cpuid_domain_info *info,
- const unsigned int *input, unsigned int
*regs)
-{
- uint64_t guest_xfeature_mask;
-
- if ( info->xfeature_mask == 0 ||
- !test_bit(X86_FEATURE_XSAVE, info->featureset) )
- {
- regs[0] = regs[1] = regs[2] = regs[3] = 0;
- return;
- }
-
- guest_xfeature_mask = X86_XCR0_SSE | X86_XCR0_X87;
-
- if ( test_bit(X86_FEATURE_AVX, info->featureset) )
- guest_xfeature_mask |= X86_XCR0_AVX;
-
- if ( test_bit(X86_FEATURE_MPX, info->featureset) )
- guest_xfeature_mask |= X86_XCR0_BNDREG | X86_XCR0_BNDCSR;
-
- if ( test_bit(X86_FEATURE_AVX512F, info->featureset) )
- guest_xfeature_mask |= X86_XCR0_OPMASK | X86_XCR0_ZMM |
X86_XCR0_HI_ZMM;
-
- if ( test_bit(X86_FEATURE_PKU, info->featureset) )
- guest_xfeature_mask |= X86_XCR0_PKRU;
-
- if ( test_bit(X86_FEATURE_LWP, info->featureset) )
- guest_xfeature_mask |= X86_XCR0_LWP;
-
- /*
- * In the common case, the toolstack will have queried Xen for the maximum
- * available featureset, and guest_xfeature_mask should not able to be
- * calculated as being greater than the host limit, info->xfeature_mask.
- *
- * Nothing currently prevents a toolstack (or an optimistic user) from
- * purposefully trying to select a larger-than-available xstate set.
- *
- * To avoid the domain dying with an unexpected fault, clamp the
- * calculated mask to the host limit. Future development work will remove
- * this possibility, when Xen fully audits the complete cpuid polcy set
- * for a domain.
- */
- guest_xfeature_mask &= info->xfeature_mask;
-
- switch ( input[1] )
- {
- case 0:
- /* EAX: low 32bits of xfeature_enabled_mask */
- regs[0] = (uint32_t)guest_xfeature_mask;
- /* EDX: high 32bits of xfeature_enabled_mask */
- regs[3] = guest_xfeature_mask >> 32;
- /* ECX: max size required by all HW features */
- {
- unsigned int _input[2] = {0xd, 0x0}, _regs[4];
- regs[2] = 0;
- for ( _input[1] = 2; _input[1] <= 62; _input[1]++ )
- {
- cpuid(_input, _regs);
- if ( (_regs[0] + _regs[1]) > regs[2] )
- regs[2] = _regs[0] + _regs[1];
- }
- }
- /* EBX: max size required by enabled features.
- * This register contains a dynamic value, which varies when a guest
- * enables or disables XSTATE features (via xsetbv). The default size
- * after reset is 576. */
- regs[1] = 512 + 64; /* FP/SSE + XSAVE.HEADER */
- break;
-
- case 1: /* leaf 1 */
- regs[0] = info->featureset[featureword_of(X86_FEATURE_XSAVEOPT)];
- regs[1] = 0;
-
- if ( test_bit(X86_FEATURE_XSAVES, info->featureset) )
- {
- regs[2] = (uint32_t)(guest_xfeature_mask & X86_XSS_MASK);
- regs[3] = (guest_xfeature_mask & X86_XSS_MASK) >> 32;
- }
- else
- regs[2] = regs[3] = 0;
- break;
-
- case 2 ... 62: /* per-component sub-leaves */
- if ( !(guest_xfeature_mask & (1ULL << input[1])) )
- {
- regs[0] = regs[1] = regs[2] = regs[3] = 0;
- break;
- }
- /* Don't touch EAX, EBX. Also cleanup ECX and EDX */
- regs[2] &= XSTATE_XSS | XSTATE_ALIGN64;
- regs[3] = 0;
- break;
-
- default:
- regs[0] = regs[1] = regs[2] = regs[3] = 0;
- break;
- }
-}
-
static void xc_cpuid_hvm_policy(xc_interface *xch,
const struct cpuid_domain_info *info,
const unsigned int *input, unsigned int *regs)
@@ -558,8 +439,12 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
regs[0] = 0;
break;
- case 0x0000000d:
- xc_cpuid_config_xsave(xch, info, input, regs);
+ case 0x0000000d: /* Xen automatically calculates almost everything. */
+ if ( input[1] == 1 )
+ regs[0] = info->featureset[featureword_of(X86_FEATURE_XSAVEOPT)];
+ else
+ regs[0] = 0;
+ regs[1] = regs[2] = regs[3] = 0;
break;
case 0x80000000:
@@ -656,8 +541,12 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
regs[0] = 0;
break;
- case 0x0000000d:
- xc_cpuid_config_xsave(xch, info, input, regs);
+ case 0x0000000d: /* Xen automatically calculates almost everything. */
+ if ( input[1] == 1 )
+ regs[0] = info->featureset[featureword_of(X86_FEATURE_XSAVEOPT)];
+ else
+ regs[0] = 0;
+ regs[1] = regs[2] = regs[3] = 0;
break;
case 0x80000000:
@@ -891,17 +780,15 @@ int xc_cpuid_apply_policy(xc_interface *xch, domid_t
domid,
continue;
}
- /* XSAVE information, subleaves 0-63. */
- if ( (input[0] == 0xd) && (input[1]++ < 63) )
- continue;
-
input[0]++;
if ( !(input[0] & 0x80000000u) && (input[0] > base_max ) )
input[0] = 0x80000000u;
input[1] = XEN_CPUID_INPUT_UNUSED;
- if ( (input[0] == 4) || (input[0] == 7) || (input[0] == 0xd) )
+ if ( (input[0] == 4) || (input[0] == 7) )
input[1] = 0;
+ else if ( input[0] == 0xd )
+ input[1] = 1; /* Xen automatically calculates almost everything. */
if ( (input[0] & 0x80000000u) && (input[0] > ext_max) )
break;
--
2.1.4
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