From: Jan Beulich <jbeulich@suse.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>, andrew.cooper3@citrix.com
Cc: iwj@xenproject.org, wl@xen.org, anthony.perard@citrix.com,
roger.pau@citrix.com, jun.nakajima@intel.com,
kevin.tian@intel.com, xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 2/4] x86: Introduce MSR_UNHANDLED
Date: Fri, 22 Jan 2021 12:51:55 +0100 [thread overview]
Message-ID: <ba472bc6-a4e4-2e94-6388-0f9bf8eef3b3@suse.com> (raw)
In-Reply-To: <1611182952-9941-3-git-send-email-boris.ostrovsky@oracle.com>
On 20.01.2021 23:49, Boris Ostrovsky wrote:
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -295,7 +295,7 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
> }
>
> /* Fallthrough. */
> - case 0x40000200 ... 0x400002ff:
> + case 0x40000200 ... 0x400002fe:
> ret = guest_rdmsr_xen(v, msr, val);
> break;
>
> @@ -514,7 +514,7 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
> }
>
> /* Fallthrough. */
> - case 0x40000200 ... 0x400002ff:
> + case 0x40000200 ... 0x400002fe:
> ret = guest_wrmsr_xen(v, msr, val);
> break;
For both of these, we need some kind of connection to
MSR_UNHANDLED. Could be a BUILD_BUG_ON() or an explicit
"case MSR_UNHANDLED:" (preventing someone "correcting" the
apparent mistake) or yet something else.
> --- a/xen/include/xen/lib/x86/msr.h
> +++ b/xen/include/xen/lib/x86/msr.h
> @@ -2,8 +2,21 @@
> #ifndef XEN_LIB_X86_MSR_H
> #define XEN_LIB_X86_MSR_H
>
> +/*
> + * Behavior on accesses to MSRs that are not handled by emulation:
> + * 0 = return #GP, warning emitted
> + * 1 = read as 0, writes are dropped, no warning
> + * 2 = read as 0, writes are dropped, warning emitted
> + */
> +#define MSR_UNHANDLED_NEVER 0
> +#define MSR_UNHANDLED_SILENT 1
> +#define MSR_UNHANDLED_VERBOSE 2
> +
> +/* MSR that is not explicitly processed by emulation */
> +#define MSR_UNHANDLED 0x400002ff
MSR indexes as well as definitions for MSR contents generally
live in asm-x86/msr-index.h. I think it would be better for
the above to also go there.
Additionally the comment on MSR_UNHANDLED should not only
say what will not happen for this index, but also what its
intended purpose is.
> @@ -45,6 +58,8 @@ struct msr_policy
> bool taa_no:1;
> };
> } arch_caps;
> +
> + uint8_t ignore_msrs;
Add a brief comment along the lines of /* MSR_UNHANDLED_* */
here to make the connection to intended values?
Also, Andrew, (I think I did say so before) - I definitely
would want your general consent with this model, as what gets
altered here is almost all relatively recent contributions
by you. Nor would I exclude the approach being controversial.
Jan
next prev parent reply other threads:[~2021-01-22 11:52 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 22:49 [PATCH v2 0/4] Permit fault-less access to non-emulated MSRs Boris Ostrovsky
2021-01-20 22:49 ` [PATCH v2 1/4] xl: Add support for ignore_msrs option Boris Ostrovsky
2021-01-21 14:56 ` Wei Liu
2021-01-21 22:43 ` Boris Ostrovsky
2021-01-22 9:52 ` Julien Grall
2021-01-22 18:28 ` Boris Ostrovsky
2021-01-22 18:33 ` Julien Grall
2021-01-22 18:39 ` Boris Ostrovsky
2021-01-22 20:42 ` Julien Grall
2021-02-18 10:42 ` Roger Pau Monné
2021-02-18 11:54 ` Jan Beulich
2021-02-18 15:52 ` Roger Pau Monné
2021-02-18 15:57 ` Jan Beulich
2021-02-19 14:50 ` Boris Ostrovsky
2021-02-22 10:24 ` Roger Pau Monné
2021-02-22 10:33 ` Jan Beulich
2021-01-20 22:49 ` [PATCH v2 2/4] x86: Introduce MSR_UNHANDLED Boris Ostrovsky
2021-01-22 11:51 ` Jan Beulich [this message]
2021-01-22 18:56 ` Boris Ostrovsky
2021-02-02 17:01 ` Boris Ostrovsky
2021-02-18 10:51 ` Roger Pau Monné
2021-02-19 14:56 ` Boris Ostrovsky
2021-02-22 11:08 ` Roger Pau Monné
2021-02-22 21:19 ` Boris Ostrovsky
2021-02-23 7:57 ` Jan Beulich
2021-02-23 9:34 ` Roger Pau Monné
2021-02-23 10:15 ` Jan Beulich
2021-02-23 12:17 ` Roger Pau Monné
2021-02-23 13:23 ` Jan Beulich
2021-02-23 15:39 ` Boris Ostrovsky
2021-02-23 16:10 ` Jan Beulich
2021-02-23 18:00 ` Roger Pau Monné
2021-02-23 16:11 ` Roger Pau Monné
2021-02-23 16:40 ` Boris Ostrovsky
2021-02-23 18:02 ` Roger Pau Monné
2021-02-23 18:45 ` Boris Ostrovsky
2021-01-20 22:49 ` [PATCH v2 3/4] x86: Allow non-faulting accesses to non-emulated MSRs if policy permits this Boris Ostrovsky
2021-01-22 12:51 ` Jan Beulich
2021-01-22 19:52 ` Boris Ostrovsky
2021-01-25 10:22 ` Jan Beulich
2021-01-25 18:42 ` Boris Ostrovsky
2021-01-26 9:05 ` Jan Beulich
2021-01-26 16:02 ` Boris Ostrovsky
2021-01-26 16:35 ` Jan Beulich
2021-02-18 11:24 ` Roger Pau Monné
2021-02-18 11:57 ` Jan Beulich
2021-02-18 15:53 ` Roger Pau Monné
2021-01-20 22:49 ` [PATCH v2 4/4] tools/libs: Apply MSR policy to a guest Boris Ostrovsky
2021-01-21 14:58 ` Wei Liu
2021-01-22 9:56 ` Julien Grall
2021-01-22 18:35 ` Boris Ostrovsky
2021-02-18 11:48 ` Roger Pau Monné
2021-02-19 14:57 ` Boris Ostrovsky
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