From: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> mainline inclusion from mainline-v6.12-rc5 commit 980c41f554c3029ce4f99678c0cd95296212775f category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IBN3WI CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------------------------------------------------------------ KVM exposes the OS double lock feature bit to Guests but returns RAZ/WI on Guest OSDLR_EL1 access. This breaks Guest migration between systems where this feature differ. Add support to make this feature writable from userspace by setting the mask bit. While at it, set the mask bits for the exposed WRPs(Number of Watchpoints) as well. Also update the selftest to cover these fields. However we still can't make BRPs and CTX_CMPs fields writable, because as per ARM ARM DDI 0487K.a, section D2.8.3 Breakpoint types and linking of breakpoints, highest numbered breakpoints(BRPs) must be context aware breakpoints(CTX_CMPs). KVM does not trap + emulate the breakpoint registers, and as such cannot support a layout that misaligns with the underlying hardware. Note: as there is no tools/testing/selftests/kvm/aarch64/set_id_regs.c in internal 6.6 kernel, remove related test part when doing backport. Reviewed-by: Oliver Upton <oliver.upton@linux.dev> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com> --- arch/arm64/kvm/sys_regs.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 77427f6990b4..041328cd978c 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2189,7 +2189,21 @@ static const struct sys_reg_desc sys_reg_descs[] = { .get_user = get_id_reg, .set_user = set_id_aa64dfr0_el1, .reset = read_sanitised_id_aa64dfr0_el1, - .val = ID_AA64DFR0_EL1_PMUVer_MASK | + /* + * Prior to FEAT_Debugv8.9, the architecture defines context-aware + * breakpoints (CTX_CMPs) as the highest numbered breakpoints (BRPs). + * KVM does not trap + emulate the breakpoint registers, and as such + * cannot support a layout that misaligns with the underlying hardware. + * While it may be possible to describe a subset that aligns with + * hardware, just prevent changes to BRPs and CTX_CMPs altogether for + * simplicity. + * + * See DDI0487K.a, section D2.8.3 Breakpoint types and linking + * of breakpoints for more details. + */ + .val = ID_AA64DFR0_EL1_DoubleLock_MASK | + ID_AA64DFR0_EL1_WRPs_MASK | + ID_AA64DFR0_EL1_PMUVer_MASK | ID_AA64DFR0_EL1_DebugVer_MASK, }, ID_SANITISED(ID_AA64DFR1_EL1), ID_UNALLOCATED(5,2), -- 2.33.0