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From: Paolo Bonzini <pbonzini@redhat.com>
To: Zixuan Wang <zixuanwang@google.com>,
	kvm@vger.kernel.org, drjones@redhat.com
Cc: marcorr@google.com, baekhw@google.com, tmroeder@google.com,
	erdemaktas@google.com, rientjes@google.com, seanjc@google.com,
	brijesh.singh@amd.com, Thomas.Lendacky@amd.com,
	varad.gautam@suse.com, jroedel@suse.de, bp@suse.de
Subject: Re: [kvm-unit-tests PATCH v2 14/17] x86 AMD SEV-ES: Load GDT with UEFI segments
Date: Mon, 20 Sep 2021 18:00:24 +0200	[thread overview]
Message-ID: <34173c4c-d704-5d28-8aac-c2debf224a86@redhat.com> (raw)
In-Reply-To: <20210827031222.2778522-15-zixuanwang@google.com>

On 27/08/21 05:12, Zixuan Wang wrote:
> + *
> + * This is because KVM-Unit-Tests reuses UEFI #VC handler that requires UEFI
> + * code and data segments to run. The UEFI #VC handler crashes the guest VM if
> + * these segments are not available. So we need to copy these two UEFI segments
> + * into KVM-Unit-Tests GDT.
> + *
> + * UEFI uses 0x30 as code segment and 0x38 as data segment. Fortunately, these
> + * segments can be safely overridden in KVM-Unit-Tests as they are used as
> + * protected mode and real mode segments (see x86/efi/efistart64.S for more
> + * details), which are not used in EFI set up process.

Is 0x30/0x38 the same as kvm-unit-tests's 0x08/0x10?  Can kvm-unit-tests
simply change its ring-0 64-bit CS/DS to 0x30 and 0x38 instead of 0x08
and 0x10?  I can help with that too, since there would be some more
shuffling to keep similar descriptors together:

  * 0x00         NULL descriptor               NULL descriptor
  * 0x08         intr_alt_stack TSS            ring-0 code segment (32-bit)
  * 0x10 (0x13)  **unused**                    ring-3 code segment (64-bit)
  * 0x18         ring-0 code segment (P=0)     ring-0 code segment (64-bit, P=0)
  * 0x20         ring-0 code segment (16-bit)  same
  * 0x28         ring-0 data segment (16-bit)  same
  * 0x30         ring-0 code segment (32-bit)  ring-0 code segment (64-bit)
  * 0x38         ring-0 data segment (32-bit)  ring-0 data segment (32/64-bit)
  * 0x40 (0x43)  ring-3 code segment (32-bit)  same
  * 0x48 (0x4b)  ring-3 data segment (32-bit)  ring-3 data segment (32/64-bit)
  * 0x50-0x78    free to use for test cases    same

or:

old	new
----	----
0x00	0x00
0x20	0x08
0x48	0x10
0x18	0x18
0x28	0x20
0x30	0x28
0x08	0x30
0x10	0x38
0x38	0x40
0x40	0x48

Thanks,

Paolo


  reply	other threads:[~2021-09-20 16:00 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27  3:12 [kvm-unit-tests PATCH v2 00/17] x86_64 UEFI and AMD SEV/SEV-ES support Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 01/17] x86 UEFI: Copy code from Linux Zixuan Wang
2021-09-20 14:33   ` Paolo Bonzini
2021-09-21  3:58     ` Zixuan Wang
2021-09-21  6:37       ` Varad Gautam
2021-09-21 16:33   ` Andrew Jones
2021-09-22 20:10     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 02/17] x86 UEFI: Implement UEFI function calls Zixuan Wang
2021-09-21 16:43   ` Andrew Jones
2021-09-22 20:17     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 03/17] x86 UEFI: Copy code from GNU-EFI Zixuan Wang
2021-10-04 12:44   ` Andrew Jones
2021-10-04 22:09     ` Zixuan Wang
2021-10-05  5:58       ` Andrew Jones
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 04/17] x86 UEFI: Boot from UEFI Zixuan Wang
2021-10-04 12:55   ` Andrew Jones
2021-10-04 21:30     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 05/17] x86 UEFI: Load IDT after UEFI boot up Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 06/17] x86 UEFI: Load GDT and TSS " Zixuan Wang
2021-09-20 15:40   ` Paolo Bonzini
2021-09-21  4:15     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 07/17] x86 UEFI: Set up memory allocator Zixuan Wang
2021-10-04 13:06   ` Andrew Jones
2021-10-04 21:43     ` Zixuan Wang
2021-10-05  6:05       ` Andrew Jones
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 08/17] x86 UEFI: Set up RSDP after UEFI boot up Zixuan Wang
2021-10-04 13:21   ` Andrew Jones
2021-10-04 21:58     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 09/17] x86 UEFI: Set up page tables Zixuan Wang
2021-09-20 15:43   ` Paolo Bonzini
2021-09-21  4:31     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 10/17] x86 UEFI: Convert x86 test cases to PIC Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 11/17] x86 AMD SEV: Initial support Zixuan Wang
2021-08-27 14:51   ` Tom Lendacky
2021-08-31 19:36     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 12/17] x86 AMD SEV: Page table with c-bit Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 13/17] x86 AMD SEV-ES: Check SEV-ES status Zixuan Wang
2021-08-27 14:55   ` Tom Lendacky
2021-08-31 19:38     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 14/17] x86 AMD SEV-ES: Load GDT with UEFI segments Zixuan Wang
2021-09-20 16:00   ` Paolo Bonzini [this message]
2021-09-21  4:41     ` Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 15/17] x86 AMD SEV-ES: Copy UEFI #VC IDT entry Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 16/17] x86 AMD SEV-ES: Set up GHCB page Zixuan Wang
2021-08-27  3:12 ` [kvm-unit-tests PATCH v2 17/17] x86 AMD SEV-ES: Add test cases Zixuan Wang
2021-10-04 13:27 ` [kvm-unit-tests PATCH v2 00/17] x86_64 UEFI and AMD SEV/SEV-ES support Andrew Jones
2021-10-04 20:54   ` Zixuan Wang

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