| Date | Thu, 24 Feb 2022 12:44:00 -0800 | From | Dave Hansen <> | Subject | Re: [PATCHv4 12/30] x86/tdx: Detect TDX at early kernel decompression time |
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On 2/24/22 07:56, Kirill A. Shutemov wrote: > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > > The early decompression code does port I/O for its console output. But, > handling the decompression-time port I/O demands a different approach > from normal runtime because the IDT required to support #VE based port > I/O emulation is not yet set up. Paravirtualizing I/O calls during > the decompression step is acceptable because the decompression code size is > small enough and hence patching it will not bloat the image size a lot.
It's not the *decompression* code size that matters. It's that there aren't a lot of call sites to the I/O instructions. Right?
> To support port I/O in decompression code, TDX must be detected before > the decompression code might do port I/O. Detect whether the kernel runs > in a TDX guest. > > Add an early_is_tdx_guest() interface to query the cached TDX guest > status in the decompression code.
Nit: I was a bit surprised by the minor cpuid() munging and the new shared/tdx.h header. They look sane, but you can reduce reviewer surprise by adding a sentence or two of changelog material.
> The actual port I/O paravirtualization will come later in the series. > > Reviewed-by: Tony Luck <tony.luck@intel.com> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
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