From: Alexey Makhalov <alexey.makhalov@broadcom.com>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux.dev,
hpa@zytor.com, dave.hansen@linux.intel.com, mingo@redhat.com,
tglx@linutronix.de, x86@kernel.org, netdev@vger.kernel.org,
richardcochran@gmail.com, linux-input@vger.kernel.org,
dmitry.torokhov@gmail.com, zackr@vmware.com,
linux-graphics-maintainer@vmware.com, pv-drivers@vmware.com,
timothym@vmware.com, akaher@vmware.com,
dri-devel@lists.freedesktop.org, daniel@ffwll.ch,
airlied@gmail.com, tzimmermann@suse.de, mripard@kernel.org,
maarten.lankhorst@linux.intel.com, horms@kernel.org,
kirill.shutemov@linux.intel.com,
Nadav Amit <nadav.amit@gmail.com>, Jeff Sipek <jsipek@vmware.com>
Subject: Re: [PATCH v9 3/8] x86/vmware: Introduce VMware hypercall API
Date: Thu, 9 May 2024 16:42:00 -0700 [thread overview]
Message-ID: <a503d8b3-d31c-46e9-a4a2-538312e850c5@broadcom.com> (raw)
In-Reply-To: <20240507095852.GVZjn7XM0VMXzBfKsd@fat_crate.local>
On 5/7/24 2:58 AM, Borislav Petkov wrote:
> On Mon, May 06, 2024 at 02:53:00PM -0700, Alexey Makhalov wrote:
>> +#define VMWARE_HYPERCALL \
>> + ALTERNATIVE_3("cmpb $" \
>> + __stringify(CPUID_VMWARE_FEATURES_ECX_VMMCALL) \
>> + ", %[mode]\n\t" \
>> + "jg 2f\n\t" \
>> + "je 1f\n\t" \
>> + "movw %[port], %%dx\n\t" \
>> + "inl (%%dx), %%eax\n\t" \
>> + "jmp 3f\n\t" \
>> + "1: vmmcall\n\t" \
>> + "jmp 3f\n\t" \
>> + "2: vmcall\n\t" \
>> + "3:\n\t", \
>> + "movw %[port], %%dx\n\t" \
>> + "inl (%%dx), %%eax", X86_FEATURE_HYPERVISOR, \
>
> That's a bunch of insns and their size would inadvertently go into the final
> image.
>
> What you should try to do is something like this:
>
> ALTERNATIVE_3("jmp .Lend_legacy_call", "", X86_FEATURE_HYPERVISOR,
> "vmcall; jmp .Lend_legacy_call", X86_FEATURE_VMCALL,
> "vmmcall; jmp .Lend_legacy_call", X86_FEATURE_VMW_VMMCALL)
>
> /* bunch of conditional branches and INs and V*MCALLs, etc go here */
>
> .Lend_legacy_call:
>
> so that you don't have these 26 bytes, as you say, of alternatives to patch but
> only the JMPs and the VM*CALLs.
>
> See for an example the macros in arch/x86/entry/calling.h which simply jump
> over the code when not needed.
Good idea!
>
> Also, you could restructure the alternative differently so that that bunch of
> insns call is completely out-of-line because all current machines support
> VM*CALL so you won't even need to patch. You only get to patch when running on
> some old rust and there you can just as well go completely out-of-line.
>
Alternatives patching has not been performed at platform detection time.
And platform detection hypercalls should work on all machines.
That is the reason we have IN as a default hypercall behavior.
> Something along those lines, anyway.
>
>> - * The high bandwidth in call. The low word of edx is presumed to have the
>> - * HB bit set.
>> + * High bandwidth calls are not supported on encrypted memory guests.
>> + * The caller should check cc_platform_has(CC_ATTR_MEM_ENCRYPT) and use
>> + * low bandwidth hypercall it memory encryption is set.
>
> s/it/if/
Acked.
>
>> -#define VMWARE_PORT(cmd, eax, ebx, ecx, edx) \
>> - __asm__("inl (%%dx), %%eax" : \
>> - "=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) : \
>> - "a"(VMWARE_HYPERVISOR_MAGIC), \
>> - "c"(VMWARE_CMD_##cmd), \
>> - "d"(VMWARE_HYPERVISOR_PORT), "b"(UINT_MAX) : \
>> - "memory")
>> -
>> -#define VMWARE_VMCALL(cmd, eax, ebx, ecx, edx) \
>> - __asm__("vmcall" : \
>> - "=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) : \
>> - "a"(VMWARE_HYPERVISOR_MAGIC), \
>> - "c"(VMWARE_CMD_##cmd), \
>> - "d"(0), "b"(UINT_MAX) : \
>> - "memory")
>> -
>> -#define VMWARE_VMMCALL(cmd, eax, ebx, ecx, edx) \
>> - __asm__("vmmcall" : \
>> - "=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) : \
>> - "a"(VMWARE_HYPERVISOR_MAGIC), \
>> - "c"(VMWARE_CMD_##cmd), \
>> - "d"(0), "b"(UINT_MAX) : \
>> - "memory")
>> -
>> -#define VMWARE_CMD(cmd, eax, ebx, ecx, edx) do { \
>> - switch (vmware_hypercall_mode) { \
>> - case CPUID_VMWARE_FEATURES_ECX_VMCALL: \
>> - VMWARE_VMCALL(cmd, eax, ebx, ecx, edx); \
>> - break; \
>> - case CPUID_VMWARE_FEATURES_ECX_VMMCALL: \
>> - VMWARE_VMMCALL(cmd, eax, ebx, ecx, edx); \
>> - break; \
>> - default: \
>> - VMWARE_PORT(cmd, eax, ebx, ecx, edx); \
>> - break; \
>> - } \
>> - } while (0)
>
> You're kidding, right?
>
> You went to all that trouble in patch 1 to move those to the header only to
> *remove* them here?
>
> You do realize that that is a unnecessary churn for no good reason, right?
>
> So that set needs to be restructured differently.
>
> * first patch introduces those new API calls.
>
> * follow-on patches convert the callers to the new API
>
> * last patch removes the old API.
>
> Ok?
My intention was to have a implementation transformation from locals
macro through common macros to common API.
What you are suggesting will eliminate unnecessary patches. It makes sense.
Will perform this restructuring in v10.
>
> And when you redo them, make sure you drop all Reviewed-by tags because the new
> versions are not reviewed anymore.
Noted.
Thanks again,
--Alexey
next prev parent reply other threads:[~2024-05-09 23:42 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-22 22:56 [PATCH v8 0/7] VMware hypercalls enhancements Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 1/7] x86/vmware: Move common macros to vmware.h Alexey Makhalov
2024-04-24 16:06 ` Borislav Petkov
2024-04-24 23:12 ` Alexey Makhalov
2024-04-24 23:14 ` [PATCH v9 1/8] x86/vmware: Correct macro names Alexey Makhalov
2024-04-24 23:14 ` [PATCH v9 2/8] x86/vmware: Move common macros to vmware.h Alexey Makhalov
2024-05-05 18:28 ` Borislav Petkov
2024-05-06 21:52 ` [PATCH v9 0/8] VMware hypercalls enhancements Alexey Makhalov
2024-05-06 21:52 ` [PATCH v9 1/8] x86/vmware: Move common macros to vmware.h Alexey Makhalov
2024-05-07 9:14 ` Borislav Petkov
2024-05-09 22:57 ` Alexey Makhalov
2024-05-06 21:52 ` [PATCH v9 2/8] x86/vmware: Correct macro names Alexey Makhalov
2024-05-06 21:53 ` [PATCH v9 3/8] x86/vmware: Introduce VMware hypercall API Alexey Makhalov
2024-05-07 9:58 ` Borislav Petkov
2024-05-09 23:42 ` Alexey Makhalov [this message]
2024-05-10 5:24 ` kernel test robot
2024-05-11 15:02 ` Simon Horman
2024-05-06 21:53 ` [PATCH v9 4/8] ptp/vmware: Use " Alexey Makhalov
2024-05-06 21:53 ` [PATCH v9 5/8] input/vmmouse: " Alexey Makhalov
2024-05-06 21:53 ` [PATCH v9 6/8] drm/vmwgfx: " Alexey Makhalov
2024-05-10 7:31 ` kernel test robot
2024-05-06 21:53 ` [PATCH v9 7/8] x86/vmware: Undefine VMWARE_HYPERCALL Alexey Makhalov
2024-05-06 21:53 ` [PATCH v9 8/8] x86/vmware: Add TDX hypercall support Alexey Makhalov
2024-04-25 15:21 ` [PATCH v9 1/8] x86/vmware: Correct macro names Borislav Petkov
2024-04-25 17:27 ` Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 2/7] x86/vmware: Introduce VMware hypercall API Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 3/7] ptp/vmware: Use " Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 4/7] input/vmmouse: " Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 5/7] drm/vmwgfx: " Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 6/7] x86/vmware: Undefine VMWARE_HYPERCALL Alexey Makhalov
2024-04-22 22:56 ` [PATCH v8 7/7] x86/vmware: Add TDX hypercall support Alexey Makhalov
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