* [PATCH v2] hvf: guard xgetbv call.
@ 2021-01-10 21:08 Hill Ma
2021-01-11 4:38 ` Roman Bolshakov
0 siblings, 1 reply; 4+ messages in thread
From: Hill Ma @ 2021-01-10 21:08 UTC (permalink / raw)
To: r.bolshakov, richard.henderson, dirty; +Cc: qemu-devel
This prevents illegal instruction on cpus do not support xgetbv.
Buglink: https://bugs.launchpad.net/qemu/+bug/1758819
Signed-off-by: Hill Ma <maahiuzeon@gmail.com>
---
v2: xgetbv() modified based on feedback.
target/i386/hvf/x86_cpuid.c | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c
index a6842912f5..edaa1b7da2 100644
--- a/target/i386/hvf/x86_cpuid.c
+++ b/target/i386/hvf/x86_cpuid.c
@@ -27,15 +27,22 @@
#include "vmx.h"
#include "sysemu/hvf.h"
-static uint64_t xgetbv(uint32_t xcr)
+static bool xgetbv(uint32_t cpuid_ecx, uint32_t idx, uint64_t *xcr)
{
- uint32_t eax, edx;
+ uint32_t xcrl, xcrh;
- __asm__ volatile ("xgetbv"
- : "=a" (eax), "=d" (edx)
- : "c" (xcr));
+ if (cpuid_ecx & CPUID_EXT_OSXSAVE) {
+ /*
+ * The xgetbv instruction is not available to older versions of
+ * the assembler, so we encode the instruction manually.
+ */
+ asm(".byte 0x0f, 0x01, 0xd0" : "=a" (xcrl), "=d" (xcrh) : "c" (idx));
- return (((uint64_t)edx) << 32) | eax;
+ *xcr = (((uint64_t)xcrh) << 32) | xcrl;
+ return true;
+ }
+
+ return false;
}
uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx,
@@ -100,11 +107,14 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx,
break;
case 0xD:
if (idx == 0) {
- uint64_t host_xcr0 = xgetbv(0);
- uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK | XSTATE_SSE_MASK |
+ uint64_t supp_xcr0 = XSTATE_FP_MASK | XSTATE_SSE_MASK |
XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK |
XSTATE_BNDCSR_MASK | XSTATE_OPMASK_MASK |
- XSTATE_ZMM_Hi256_MASK | XSTATE_Hi16_ZMM_MASK);
+ XSTATE_ZMM_Hi256_MASK | XSTATE_Hi16_ZMM_MASK;
+ uint64_t host_xcr0;
+ if (xgetbv(ecx, 0, &host_xcr0)) {
+ supp_xcr0 &= host_xcr0;
+ }
eax &= supp_xcr0;
} else if (idx == 1) {
hv_vmx_read_capability(HV_VMX_CAP_PROCBASED2, &cap);
--
2.20.1 (Apple Git-117)
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2] hvf: guard xgetbv call.
2021-01-10 21:08 [PATCH v2] hvf: guard xgetbv call Hill Ma
@ 2021-01-11 4:38 ` Roman Bolshakov
2021-01-12 5:44 ` Hill Ma
0 siblings, 1 reply; 4+ messages in thread
From: Roman Bolshakov @ 2021-01-11 4:38 UTC (permalink / raw)
To: Hill Ma; +Cc: richard.henderson, qemu-devel, dirty
On Sun, Jan 10, 2021 at 01:08:54PM -0800, Hill Ma wrote:
> This prevents illegal instruction on cpus do not support xgetbv.
>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1758819
> Signed-off-by: Hill Ma <maahiuzeon@gmail.com>
> ---
> v2: xgetbv() modified based on feedback.
>
> target/i386/hvf/x86_cpuid.c | 28 +++++++++++++++++++---------
> 1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c
> index a6842912f5..edaa1b7da2 100644
> --- a/target/i386/hvf/x86_cpuid.c
> +++ b/target/i386/hvf/x86_cpuid.c
> @@ -27,15 +27,22 @@
> #include "vmx.h"
> #include "sysemu/hvf.h"
>
> -static uint64_t xgetbv(uint32_t xcr)
> +static bool xgetbv(uint32_t cpuid_ecx, uint32_t idx, uint64_t *xcr)
> {
> - uint32_t eax, edx;
> + uint32_t xcrl, xcrh;
>
> - __asm__ volatile ("xgetbv"
> - : "=a" (eax), "=d" (edx)
> - : "c" (xcr));
> + if (cpuid_ecx & CPUID_EXT_OSXSAVE) {
> + /*
> + * The xgetbv instruction is not available to older versions of
> + * the assembler, so we encode the instruction manually.
> + */
> + asm(".byte 0x0f, 0x01, 0xd0" : "=a" (xcrl), "=d" (xcrh) : "c" (idx));
>
> - return (((uint64_t)edx) << 32) | eax;
> + *xcr = (((uint64_t)xcrh) << 32) | xcrl;
> + return true;
> + }
> +
> + return false;
> }
>
> uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx,
> @@ -100,11 +107,14 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx,
> break;
> case 0xD:
> if (idx == 0) {
> - uint64_t host_xcr0 = xgetbv(0);
> - uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK | XSTATE_SSE_MASK |
> + uint64_t supp_xcr0 = XSTATE_FP_MASK | XSTATE_SSE_MASK |
> XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK |
> XSTATE_BNDCSR_MASK | XSTATE_OPMASK_MASK |
> - XSTATE_ZMM_Hi256_MASK | XSTATE_Hi16_ZMM_MASK);
> + XSTATE_ZMM_Hi256_MASK | XSTATE_Hi16_ZMM_MASK;
> + uint64_t host_xcr0;
> + if (xgetbv(ecx, 0, &host_xcr0)) {
> + supp_xcr0 &= host_xcr0;
Hi Hill,
I'm not sure if eax should be modified with mask because the mask has no
value per se. I.e. eax &= supp_xcr0 from below should be placed inside
the if. It'd express clearly that eax is not modified unless xgetbv is
supported.
Thanks,
Roman
> + }
> eax &= supp_xcr0;
> } else if (idx == 1) {
> hv_vmx_read_capability(HV_VMX_CAP_PROCBASED2, &cap);
> --
> 2.20.1 (Apple Git-117)
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] hvf: guard xgetbv call.
2021-01-11 4:38 ` Roman Bolshakov
@ 2021-01-12 5:44 ` Hill Ma
2021-01-12 7:46 ` Roman Bolshakov
0 siblings, 1 reply; 4+ messages in thread
From: Hill Ma @ 2021-01-12 5:44 UTC (permalink / raw)
To: Roman Bolshakov; +Cc: richard.henderson, qemu-devel, dirty
On Sun, Jan 10, 2021 at 8:38 PM Roman Bolshakov <r.bolshakov@yadro.com> wrote:
> I'm not sure if eax should be modified with mask because the mask has no
> value per se. I.e. eax &= supp_xcr0 from below should be placed inside
> the if. It'd express clearly that eax is not modified unless xgetbv is
> supported.
Like this?
- uint64_t host_xcr0 = xgetbv(0);
- uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK |
XSTATE_SSE_MASK |
+ uint64_t host_xcr0;
+ if (xgetbv(ecx, 0, &host_xcr0)) {
+ uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK |
XSTATE_SSE_MASK |
XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK |
XSTATE_BNDCSR_MASK | XSTATE_OPMASK_MASK |
XSTATE_ZMM_Hi256_MASK |
XSTATE_Hi16_ZMM_MASK);
- eax &= supp_xcr0;
+ eax &= supp_xcr0;
+ }
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] hvf: guard xgetbv call.
2021-01-12 5:44 ` Hill Ma
@ 2021-01-12 7:46 ` Roman Bolshakov
0 siblings, 0 replies; 4+ messages in thread
From: Roman Bolshakov @ 2021-01-12 7:46 UTC (permalink / raw)
To: Hill Ma; +Cc: richard.henderson, qemu-devel, dirty
On Mon, Jan 11, 2021 at 09:44:40PM -0800, Hill Ma wrote:
> On Sun, Jan 10, 2021 at 8:38 PM Roman Bolshakov <r.bolshakov@yadro.com> wrote:
> > I'm not sure if eax should be modified with mask because the mask has no
> > value per se. I.e. eax &= supp_xcr0 from below should be placed inside
> > the if. It'd express clearly that eax is not modified unless xgetbv is
> > supported.
>
> Like this?
>
> - uint64_t host_xcr0 = xgetbv(0);
> - uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK |
> XSTATE_SSE_MASK |
> + uint64_t host_xcr0;
> + if (xgetbv(ecx, 0, &host_xcr0)) {
> + uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK |
> XSTATE_SSE_MASK |
> XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK |
> XSTATE_BNDCSR_MASK | XSTATE_OPMASK_MASK |
> XSTATE_ZMM_Hi256_MASK |
> XSTATE_Hi16_ZMM_MASK);
> - eax &= supp_xcr0;
> + eax &= supp_xcr0;
> + }
Yes.
Thanks,
Roman
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-01-10 21:08 [PATCH v2] hvf: guard xgetbv call Hill Ma
2021-01-11 4:38 ` Roman Bolshakov
2021-01-12 5:44 ` Hill Ma
2021-01-12 7:46 ` Roman Bolshakov
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