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Sean Christopherson 842f4be958 KVM: VMX: Add a trampoline to fix VMREAD error handling 
Add a hand coded assembly trampoline to preserve volatile registers
across vmread_error(), and to handle the calling convention differences
between 64-bit and 32-bit due to asmlinkage on vmread_error().  Pass
@field and @fault on the stack when invoking the trampoline to avoid
clobbering volatile registers in the context of the inline assembly.

Calling vmread_error() directly from inline assembly is partially broken
on 64-bit, and completely broken on 32-bit.  On 64-bit, it will clobber
%rdi and %rsi (used to pass @field and @fault) and any volatile regs
written by vmread_error().  On 32-bit, asmlinkage means vmread_error()
expects the parameters to be passed on the stack, not via regs.

Opportunistically zero out the result in the trampoline to save a few
bytes of code for every VMREAD.  A happy side effect of the trampoline
is that the inline code footprint is reduced by three bytes on 64-bit
due to PUSH/POP being more efficent (in terms of opcode bytes) than MOV.

Fixes: 6e2020977e ("KVM: VMX: Add error handling to VMREAD helper")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200326160712.28803-1-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-03-31 10:48:11 -04:00
arch KVM: VMX: Add a trampoline to fix VMREAD error handling 2020-03-31 10:48:11 -04:00
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Documentation KVM PPC update for 5.7 2020-03-31 10:45:49 -04:00
drivers irqchip/gic-v4.1: Eagerly vmap vPEs 2020-03-24 12:15:51 +00:00
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include KVM: Pass kvm_init()'s opaque param to additional arch funcs 2020-03-31 10:48:03 -04:00
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tools KVM/arm updates for Linux 5.7 2020-03-31 10:44:53 -04:00
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virt KVM: Pass kvm_init()'s opaque param to additional arch funcs 2020-03-31 10:48:03 -04:00
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MAINTAINERS KVM/arm updates for Linux 5.7 2020-03-31 10:44:53 -04:00
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README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.