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a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1603807885; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=j/2Q2d4NLk5j8Y791XgkMADfxqAFxYy385J6xuXYUOw=; b=M4suCh9dq3aBwLOke6796Ynu9v14vrEdH+qWDBJ1iB+9Nl+aNu+QlFqP 2aZIPnNAEK6MSovbJMZHrVVNuZLlaDPoDbE3GxxvVqazbd3dSPXVZz3NB /3GGV+z8AkZiZDifek5IdCZG0kAyIXqaPFv3QNApsKuiY2Mt5qW9bT4gC Q=; Authentication-Results: esa4.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: i3Xm9+72s+9SQAOfx/iEGcWF1xIlG8CV0kUKezAnXuNKS58307q0HDGBAIRxOYiSR6oj2TAX7Z yyxP6oPGngkVI/RSyARHYtmLw5SK3Z2ab8/WkrGSGJQDx3UJbZiVToh6oRsBIMjoP+5v4V1NrN QU9LWJSvCkwGshznU1Hi8muDhcOu2Wb/mJnVWSXZExzZYXyDFAayF+U+tRi7ROpfV8+f64FcLo xQ02QPUbzInVvX/dx6tG+ds9ETC8jtChebXeBGHoaCW9O/n1r89xzuU1wA9eyp1hL7BAvamhxW 4oY= X-SBRS: None X-MesageID: 30949880 X-Ironport-Server: esa4.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.77,424,1596513600"; d="scan'208";a="30949880" From: Andrew Cooper To: Xen-devel CC: Andrew Cooper , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Wei Liu Subject: [PATCH v3 1/2] x86/pv: Drop FLUSH_TLB_GLOBAL in do_mmu_update() for XPTI Date: Tue, 27 Oct 2020 14:10:36 +0000 Message-ID: <20201027141037.27357-2-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20201027141037.27357-1-andrew.cooper3@citrix.com> References: <20201027141037.27357-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @citrix.com) c/s 9d1d31ad9498 "x86: slightly reduce Meltdown band-aid overhead" removed = the use of Global TLB flushes on the Xen entry path, but added a FLUSH_TLB_GLOB= AL to the L4 path in do_mmu_update(). However, this was unnecessary. The L4 resync will pick up any new mappings created by the L4 change. Any changes to existing mappings are the guests responsibility to flush, and if one is needed, an MMUEXT_OP hypercall will follow. This is (not really) XSA-286 (but necessary to simplify the logic). Fixes: 9d1d31ad9498 ("x86: slightly reduce Meltdown band-aid overhead") Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- CC: Jan Beulich CC: Roger Pau Monn=C3=A9 CC: Wei Liu v3: * New --- xen/arch/x86/mm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index b2f35b3e7d..38168189aa 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -4188,7 +4188,7 @@ long do_mmu_update( =20 cpumask_andnot(mask, pt_owner->dirty_cpumask, cpumask_of(cpu)); if ( !cpumask_empty(mask) ) - flush_mask(mask, FLUSH_TLB_GLOBAL | FLUSH_ROOT_PGTBL); + flush_mask(mask, FLUSH_ROOT_PGTBL); } =20 perfc_add(num_page_updates, i); --=20 2.11.0