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Re: [PATCH v2 5/8] x86/hvm: Context switch MSR_PKRS
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 12 Jan 2023 14:10:57 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 12 Jan 2023 13:11:15 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 10.01.2023 18:18, Andrew Cooper wrote:
> +static inline void wrpkrs(uint32_t pkrs)
> +{
> + uint32_t *this_pkrs = &this_cpu(pkrs);
> +
> + if ( *this_pkrs != pkrs )
> + {
> + *this_pkrs = pkrs;
> +
> + wrmsr_ns(MSR_PKRS, pkrs, 0);
> + }
> +}
> +
> +static inline void wrpkrs_and_cache(uint32_t pkrs)
> +{
> + this_cpu(pkrs) = pkrs;
> + wrmsr_ns(MSR_PKRS, pkrs, 0);
> +}
Just to confirm - there's no anticipation of uses of this in async
contexts, i.e. there's no concern about the ordering of cache vs hardware
writes?
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -54,6 +54,7 @@
> #include <asm/spec_ctrl.h>
> #include <asm/guest.h>
> #include <asm/microcode.h>
> +#include <asm/prot-key.h>
> #include <asm/pv/domain.h>
>
> /* opt_nosmp: If true, secondary processors are ignored. */
> @@ -1804,6 +1805,9 @@ void __init noreturn __start_xen(unsigned long mbi_p)
> if ( opt_invpcid && cpu_has_invpcid )
> use_invpcid = true;
>
> + if ( cpu_has_pks )
> + wrpkrs_and_cache(0); /* Must be before setting CR4.PKS */
Same question here as for PKRU wrt the BSP during S3 resume.
Jan
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