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Re: [Xen-devel] [PATCH v4 1/2] xen/arm: remove physical timer offset
On 24/01/2020 21:43, Jeff Kubascik wrote:
On 1/23/2020 7:32 AM, Julien Grall wrote:
Hi,
On 21/01/2020 15:07, Jeff Kubascik wrote:
The physical timer traps apply an offset so that time starts at 0 for
the guest. However, this offset is not currently applied to the physical
counter. Per the ARMv8 Reference Manual (ARM DDI 0487E.a), section
D11.2.4 Timers, the "Offset" between the counter and timer should be
zero for a physical timer. This removes the offset to make the timer and
counter consistent.
This also cleans up the physical timer implementation to better match
the virtual timer - both cval's now hold the hardware value.
Signed-off-by: Jeff Kubascik <jeff.kubascik@xxxxxxxxxxxxxxx>
---
xen/arch/arm/vtimer.c | 34 ++++++++++++++++++----------------
xen/include/asm-arm/domain.h | 3 ---
2 files changed, 18 insertions(+), 19 deletions(-)
diff --git a/xen/arch/arm/vtimer.c b/xen/arch/arm/vtimer.c
index 240a850b6e..0c78a65863 100644
--- a/xen/arch/arm/vtimer.c
+++ b/xen/arch/arm/vtimer.c
@@ -62,7 +62,6 @@ static void virt_timer_expired(void *data)
int domain_vtimer_init(struct domain *d, struct xen_arch_domainconfig
*config)
{
- d->arch.phys_timer_base.offset = NOW();
d->arch.virt_timer_base.offset = READ_SYSREG64(CNTPCT_EL0);
d->time_offset.seconds = ticks_to_ns(d->arch.virt_timer_base.offset -
boot_count);
do_div(d->time_offset.seconds, 1000000000);
@@ -108,7 +107,6 @@ int vcpu_vtimer_init(struct vcpu *v)
init_timer(&t->timer, phys_timer_expired, t, v->processor);
t->ctl = 0;
- t->cval = NOW();
t->irq = d0
? timer_get_irq(TIMER_PHYS_NONSECURE_PPI)
: GUEST_TIMER_PHYS_NS_PPI;
@@ -167,6 +165,7 @@ void virt_timer_restore(struct vcpu *v)
static bool vtimer_cntp_ctl(struct cpu_user_regs *regs, uint32_t *r, bool
read)
{
struct vcpu *v = current;
+ s_time_t expires;
if ( !ACCESS_ALLOWED(regs, EL0PTEN) )
return false;
@@ -184,8 +183,9 @@ static bool vtimer_cntp_ctl(struct cpu_user_regs *regs,
uint32_t *r, bool read)
if ( v->arch.phys_timer.ctl & CNTx_CTL_ENABLE )
{
- set_timer(&v->arch.phys_timer.timer,
- v->arch.phys_timer.cval +
v->domain->arch.phys_timer_base.offset);
+ expires = v->arch.phys_timer.cval > boot_count
+ ? ticks_to_ns(v->arch.phys_timer.cval - boot_count) : 0;
+ set_timer(&v->arch.phys_timer.timer, expires);
While the factoring was optional, my request of a comment wasn't (even
if it requires to duplicate 3 times).
Understood.
If you suggest a comment and an update of the commit message, I can
merge it in this patch on commit.
For the comment:
/* If cval is before the point Xen started, expire timer immediately */
For the commit message:
In the case the guest sets cval to a time before Xen started, the correct
behavior is to expire the timer immediately. To do this, we set the expires
argument of set_timer to zero.
It looks good to me, I will commit the series on Monday. Thanks!
Cheers,
--
Julien Grall
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