[gentoo-commits] proj/linux-patches:5.10 commit in: /

[Alice Ferrazzi]

commit:     0516d30fad4f3ec1e6c5f821a798c695034f77f5
Author:     Alice Ferrazzi <alicef <AT> gentoo <DOT> org>
AuthorDate: Thu Jul  8 03:23:26 2021 +0000
Commit:     Alice Ferrazzi <alicef <AT> gentoo <DOT> org>
CommitDate: Thu Jul  8 03:26:38 2021 +0000
URL:        https://gitweb.gentoo.org/proj/linux-patches.git/commit/?id=0516d30f

Add KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path

Signed-off-by: Alice Ferrazzi <alicef <AT> gentoo.org>

 0000_README                         |  4 +++
 1700_P9_save_and_restore_fscr.patch | 56 +++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/0000_README b/0000_README
index dc7b9b6..aefbc8e 100644
--- a/0000_README
+++ b/0000_README
@@ -243,6 +243,10 @@ Patch:  1510_fs-enable-link-security-restrictions-by-default.patch
 From:   http://sources.debian.net/src/linux/3.16.7-ckt4-3/debian/patches/debian/fs-enable-link-security-restrictions-by-default.patch/
 Desc:   Enable link security restrictions by default.
 
+Patch:  1700_P9_save_and_restore_fscr.patch
+From:   https://github.com/torvalds/linux/commit/25edcc50d76c.patch
+Desc:   Fix qemu on P9 ppc64.
+
 Patch:  2000_BT-Check-key-sizes-only-if-Secure-Simple-Pairing-enabled.patch
 From:   https://lore.kernel.org/linux-bluetooth/20190522070540.48895-1-marcel@××××××××.org/raw
 Desc:   Bluetooth: Check key sizes only when Secure Simple Pairing is enabled. See bug #686758

diff --git a/1700_P9_save_and_restore_fscr.patch b/1700_P9_save_and_restore_fscr.patch
new file mode 100644
index 0000000..59a7c7e
--- /dev/null
+++ b/1700_P9_save_and_restore_fscr.patch
@@ -0,0 +1,56 @@
+From 25edcc50d76c834479d11fcc7de46f3da4d95121 Mon Sep 17 00:00:00 2001
+From: Fabiano Rosas <farosas@×××××××××.com>
+Date: Thu, 4 Feb 2021 17:05:17 -0300
+Subject: [PATCH] KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path
+
+The Facility Status and Control Register is a privileged SPR that
+defines the availability of some features in problem state. Since it
+can be written by the guest, we must restore it to the previous host
+value after guest exit.
+
+This restoration is currently done by taking the value from
+current->thread.fscr, which in the P9 path is not enough anymore
+because the guest could context switch the QEMU thread, causing the
+guest-current value to be saved into the thread struct.
+
+The above situation manifested when running a QEMU linked against a
+libc with System Call Vectored support, which causes scv
+instructions to be run by QEMU early during the guest boot (during
+SLOF), at which point the FSCR is 0 due to guest entry. After a few
+scv calls (1 to a couple hundred), the context switching happens and
+the QEMU thread runs with the guest value, resulting in a Facility
+Unavailable interrupt.
+
+This patch saves and restores the host value of FSCR in the inner
+guest entry loop in a way independent of current->thread.fscr. The old
+way of doing it is still kept in place because it works for the old
+entry path.
+
+Signed-off-by: Fabiano Rosas <farosas@×××××××××.com>
+Signed-off-by: Paul Mackerras <paulus@××××××.org>
+---
+ arch/powerpc/kvm/book3s_hv.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
+index 89c686c17f0606..f6d470157fcb62 100644
+--- a/arch/powerpc/kvm/book3s_hv.c
++++ b/arch/powerpc/kvm/book3s_hv.c
+@@ -3611,6 +3611,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
+ 	unsigned long host_tidr = mfspr(SPRN_TIDR);
+ 	unsigned long host_iamr = mfspr(SPRN_IAMR);
+ 	unsigned long host_amr = mfspr(SPRN_AMR);
++	unsigned long host_fscr = mfspr(SPRN_FSCR);
+ 	s64 dec;
+ 	u64 tb;
+ 	int trap, save_pmu;
+@@ -3751,6 +3752,9 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
+ 	if (host_amr != vcpu->arch.amr)
+ 		mtspr(SPRN_AMR, host_amr);
+ 
++	if (host_fscr != vcpu->arch.fscr)
++		mtspr(SPRN_FSCR, host_fscr);
++
+ 	msr_check_and_set(MSR_FP | MSR_VEC | MSR_VSX);
+ 	store_fp_state(&vcpu->arch.fp);
+ #ifdef CONFIG_ALTIVEC