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Re: [PATCH v2 5/8] x86/hvm: Context switch MSR_PKRS
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- Date: Mon, 16 Jan 2023 13:00:18 +0000
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- Cc: Roger Pau Monne <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHZJRefeExwWeppzE65VXS63DgRAq6axG6AgAA9twCABgijAA==
- Thread-topic: [PATCH v2 5/8] x86/hvm: Context switch MSR_PKRS
On 12/01/2023 4:51 pm, Andrew Cooper wrote:
> On 12/01/2023 1:10 pm, Jan Beulich wrote:
>> On 10.01.2023 18:18, Andrew Cooper wrote:
>>> --- 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.
> I had reasoned not, but it turns out that I'm wrong.
>
> It's important to reset the cache back to 0 here. (Handling PKRU is
> different - I'll follow up on the other email..)
diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index d23335391c67..de9317e8c573 100644
--- a/xen/arch/x86/acpi/power.c
+++ b/xen/arch/x86/acpi/power.c
@@ -299,6 +299,13 @@ static int enter_state(u32 state)
update_mcu_opt_ctrl();
+ /*
+ * Should be before restoring CR4, but that is earlier in asm. We
rely on
+ * MSR_PKRS actually being 0 out of S3 resume.
+ */
+ if ( cpu_has_pks )
+ wrpkrs_and_cache(0);
+
/* (re)initialise SYSCALL/SYSENTER state, amongst other things. */
percpu_traps_init();
I've folded this hunk, to sort out the S3 resume path.
As its the final hunk before the entire series can be committed, I
shan't bother sending a v3 just for this.
~Andrew
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