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Date: Wed, 3 Jan 2024 16:24:02 +0000
From: Simon Horman <horms@kernel.org>
To: Alexey Makhalov <alexey.makhalov@broadcom.com>
Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux.dev,
	bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com,
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	linux-input@vger.kernel.org, dmitry.torokhov@gmail.com,
	zackr@vmware.com, linux-graphics-maintainer@vmware.com,
	pv-drivers@vmware.com, namit@vmware.com, timothym@vmware.com,
	akaher@vmware.com, jsipek@vmware.com,
	dri-devel@lists.freedesktop.org, daniel@ffwll.ch, airlied@gmail.com,
	tzimmermann@suse.de, mripard@kernel.org,
	maarten.lankhorst@linux.intel.com, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v4 2/6] x86/vmware: Introduce VMware hypercall API
Message-ID: <20240103162402.GA31813@kernel.org>
References: <20231228192421.29894-1-alexey.makhalov@broadcom.com>
 <20231228192421.29894-3-alexey.makhalov@broadcom.com>
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In-Reply-To: <20231228192421.29894-3-alexey.makhalov@broadcom.com>

On Thu, Dec 28, 2023 at 11:24:17AM -0800, Alexey Makhalov wrote:
> From: Alexey Makhalov <amakhalov@vmware.com>
> 
> Introduce vmware_hypercall family of functions. It is a common
> implementation to be used by the VMware guest code and virtual
> device drivers in architecture independent manner.
> 
> The API consists of vmware_hypercallX and vmware_hypercall_hb_{out,in}
> set of functions by analogy with KVM hypercall API. Architecture
> specific implementation is hidden inside.
> 
> It will simplify future enhancements in VMware hypercalls such
> as SEV-ES and TDX related changes without needs to modify a
> caller in device drivers code.
> 
> Current implementation extends an idea from commit bac7b4e84323
> ("x86/vmware: Update platform detection code for VMCALL/VMMCALL
> hypercalls") to have a slow, but safe path in VMWARE_HYPERCALL
> earlier during the boot when alternatives are not yet applied.
> This logic was inherited from VMWARE_CMD from the commit mentioned
> above. Default alternative code was optimized by size to reduce
> excessive nop alignment once alternatives are applied. Total
> default code size is 26 bytes, in worse case (3 bytes alternative)
> remaining 23 bytes will be aligned by only 3 long NOP instructions.
> 
> Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
> Reviewed-by: Nadav Amit <namit@vmware.com>
> Reviewed-by: Jeff Sipek <jsipek@vmware.com>

Hi Alexey,

I'd like to flag that this breaks gcc-13 x86_64 allmodconfig builds of the
following files. And although this is resolved by the subsequent 3 patches
in this series, it does still break bisection.

 drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
 drivers/input/mouse/vmmouse.c
 drivers/ptp/ptp_vmw.c

...