On 10/03/20 04:54, Sean Christopherson wrote:
> Track the last known CR0, CR4, and EFER values in the access test to
> avoid taking a VM-Exit on every. single. test. The EFER VM-Exits in
> particular absolutely tank performance when running the test in L1.
>
> Opportunistically tweak the 5-level test to print that it's starting
> before configuring 5-level page tables, e.g. in case enabling 5-level
> paging runs into issues.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> x86/access.c | 45 +++++++++++++++++++++++++++------------------
> 1 file changed, 27 insertions(+), 18 deletions(-)
>
> diff --git a/x86/access.c b/x86/access.c
> index 7303fc3..86d8a72 100644
> --- a/x86/access.c
> +++ b/x86/access.c
> @@ -169,29 +169,33 @@ typedef struct {
>
> static void ac_test_show(ac_test_t *at);
>
> +static unsigned long shadow_cr0;
> +static unsigned long shadow_cr4;
> +static unsigned long long shadow_efer;
> +
> static void set_cr0_wp(int wp)
> {
> - unsigned long cr0 = read_cr0();
> - unsigned long old_cr0 = cr0;
> + unsigned long cr0 = shadow_cr0;
>
> cr0 &= ~CR0_WP_MASK;
> if (wp)
> cr0 |= CR0_WP_MASK;
> - if (old_cr0 != cr0)
> + if (cr0 != shadow_cr0) {
> write_cr0(cr0);
> + shadow_cr0 = cr0;
> + }
> }
>
> static unsigned set_cr4_smep(int smep)
> {
> - unsigned long cr4 = read_cr4();
> - unsigned long old_cr4 = cr4;
> + unsigned long cr4 = shadow_cr4;
> extern u64 ptl2[];
> unsigned r;
>
> cr4 &= ~CR4_SMEP_MASK;
> if (smep)
> cr4 |= CR4_SMEP_MASK;
> - if (old_cr4 == cr4)
> + if (cr4 == shadow_cr4)
> return 0;
>
> if (smep)
> @@ -199,37 +203,39 @@ static unsigned set_cr4_smep(int smep)
> r = write_cr4_checking(cr4);
> if (r || !smep)
> ptl2[2] |= PT_USER_MASK;
> + if (!r)
> + shadow_cr4 = cr4;
> return r;
> }
>
> static void set_cr4_pke(int pke)
> {
> - unsigned long cr4 = read_cr4();
> - unsigned long old_cr4 = cr4;
> + unsigned long cr4 = shadow_cr4;
>
> cr4 &= ~X86_CR4_PKE;
> if (pke)
> cr4 |= X86_CR4_PKE;
> - if (old_cr4 == cr4)
> + if (cr4 == shadow_cr4)
> return;
>
> /* Check that protection keys do not affect accesses when CR4.PKE=0. */
> - if ((read_cr4() & X86_CR4_PKE) && !pke) {
> + if ((shadow_cr4 & X86_CR4_PKE) && !pke)
> write_pkru(0xfffffffc);
> - }
> write_cr4(cr4);
> + shadow_cr4 = cr4;
> }
>
> static void set_efer_nx(int nx)
> {
> - unsigned long long efer = rdmsr(MSR_EFER);
> - unsigned long long old_efer = efer;
> + unsigned long long efer = shadow_efer;
>
> efer &= ~EFER_NX_MASK;
> if (nx)
> efer |= EFER_NX_MASK;
> - if (old_efer != efer)
> + if (efer != shadow_efer) {
> wrmsr(MSR_EFER, efer);
> + shadow_efer = efer;
> + }
> }
>
> static void ac_env_int(ac_pool_t *pool)
> @@ -245,7 +251,7 @@ static void ac_env_int(ac_pool_t *pool)
>
> static void ac_test_init(ac_test_t *at, void *virt)
> {
> - wrmsr(MSR_EFER, rdmsr(MSR_EFER) | EFER_NX_MASK);
> + set_efer_nx(1);
> set_cr0_wp(1);
> at->flags = 0;
> at->virt = virt;
> @@ -935,14 +941,17 @@ static int ac_test_run(void)
> printf("run\n");
> tests = successes = 0;
>
> + shadow_cr0 = read_cr0();
> + shadow_cr4 = read_cr4();
> + shadow_efer = rdmsr(MSR_EFER);
> +
> if (this_cpu_has(X86_FEATURE_PKU)) {
> set_cr4_pke(1);
> set_cr4_pke(0);
> /* Now PKRU = 0xFFFFFFFF. */
> } else {
> - unsigned long cr4 = read_cr4();
> tests++;
> - if (write_cr4_checking(cr4 | X86_CR4_PKE) == GP_VECTOR) {
> + if (write_cr4_checking(shadow_cr4 | X86_CR4_PKE) == GP_VECTOR) {
> successes++;
> invalid_mask |= AC_PKU_AD_MASK;
> invalid_mask |= AC_PKU_WD_MASK;
> @@ -996,8 +1005,8 @@ int main(void)
>
> if (this_cpu_has(X86_FEATURE_LA57)) {
> page_table_levels = 5;
> - setup_5level_page_table();
> printf("starting 5-level paging test.\n\n");
> + setup_5level_page_table();
> r = ac_test_run();
> }
>
>
Applied all three patches, thanks.
Paolo
