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SubjectRe: [PATCHv6 04/11] x86/mm: Handle LAM on context switch
On Mon, Aug 15, 2022 at 07:17:56AM +0300, Kirill A. Shutemov wrote:
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index c1e31e9a85d7..fdc0b69b5da7 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -154,17 +154,18 @@ static inline u16 user_pcid(u16 asid)
> return ret;
> }
>
> -static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
> +static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
> {
> if (static_cpu_has(X86_FEATURE_PCID)) {
> - return __sme_pa(pgd) | kern_pcid(asid);
> + return __sme_pa(pgd) | kern_pcid(asid) | lam;
> } else {
> VM_WARN_ON_ONCE(asid != 0);
> - return __sme_pa(pgd);
> + return __sme_pa(pgd) | lam;
> }
> }
>
> -static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
> +static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
> + unsigned long lam)
> {
> VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
> /*
> @@ -173,7 +174,7 @@ static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
> * boot because all CPU's the have same capabilities:
> */
> VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
> - return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
> + return __sme_pa(pgd) | kern_pcid(asid) | lam | CR3_NOFLUSH;
> }

Looking at this; I wonder if we want something like this:

--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -157,6 +157,7 @@ static inline u16 user_pcid(u16 asid)
static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
{
if (static_cpu_has(X86_FEATURE_PCID)) {
+ VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
return __sme_pa(pgd) | kern_pcid(asid) | lam;
} else {
VM_WARN_ON_ONCE(asid != 0);
@@ -167,14 +168,13 @@ static inline unsigned long build_cr3(pg
static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
unsigned long lam)
{
- VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
/*
* Use boot_cpu_has() instead of this_cpu_has() as this function
* might be called during early boot. This should work even after
* boot because all CPU's the have same capabilities:
*/
VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
- return __sme_pa(pgd) | kern_pcid(asid) | lam | CR3_NOFLUSH;
+ return build_cr3(pgd, asid, lam) | CR3_NOFLUSH;
}

/*
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