On Wed, Jul 06, 2016 at 03:43:16PM +0200, Paolo Bonzini wrote:
> I don't know what I was thinking when I wrote commit 46896c73c1a4 ("KVM:
> svm: add support for RDTSCP", 2015-11-12); I missed write_rdtscp_aux which
> obviously uses MSR_TSC_AUX.
>
> Therefore we do need to save/restore MSR_TSC_AUX in svm_vcpu_run.
>
> Cc: sta...@vger.kernel.org
> Cc: Borislav Petkov <b...@alien8.de>
> Fixes: 46896c73c1a4 ("KVM: svm: add support for RDTSCP")
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Something's still missing. I have a small program which does RDTSCP in
the guest:
$ taskset -c 3 ./rdtscp
aux1: 0x0
aux2: 0x0
p1: 195514968442, p2: 195515255582, 287140
and the aux things which are %ecx, are 0 (should be 3 in that case).
It did work with my patch with the RDTSCP intercept:
$ taskset -c 3 ./rdtscp
aux1: 0x3
aux2: 0x3
p1: 157117003683, p2: 157119280794, 2277111
Btw, just for my own understanding: if we don't intercept RDTSCP, does
it get emulated? Where does the TSC value come from, qemu?
Here's the program.
---
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
typedef unsigned long long u64;
#define DECLARE_ARGS(val, low, high) unsigned low, high
#define EAX_EDX_VAL(val, low, high) ((low) | ((u64)(high) << 32))
#define EAX_EDX_ARGS(val, low, high) "a" (low), "d" (high)
#define EAX_EDX_RET(val, low, high) "=a" (low), "=d" (high)
static __always_inline unsigned long long rdtscp(unsigned int *aux)
{
unsigned int lo, hi;
asm volatile("rdtscp" : "=a" (lo), "=d" (hi), "=c" (*aux));
return EAX_EDX_VAL(0, lo, hi);
}
int main()
{
unsigned long long p1, p2;
unsigned int aux;
p1 = rdtscp(&aux);
printf("aux1: 0x%x\n", aux);
p2 = rdtscp(&aux);
printf("aux2: 0x%x\n", aux);
printf("p1: %llu, p2: %llu, %lld\n", p1, p2, p2 - p1);
return 0;
}
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
