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Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:46962) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ikoCM-0001BR-E3; Fri, 27 Dec 2019 11:54:30 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1ikoCJ-0004ee-VR; Fri, 27 Dec 2019 11:54:27 +0000 Date: Fri, 27 Dec 2019 11:54:27 +0000 From: Russell King - ARM Linux admin To: Marc Zyngier Subject: Re: [PATCH] arm64: kvm: fix IDMAP overlap with HYP VA Message-ID: <20191227115427.GV25745@shell.armlinux.org.uk> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191227_035643_440800_F0249B9F X-CRM114-Status: GOOD ( 25.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Suzuki K Poulose , Catalin Marinas , James Morse , Julien Thierry , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Dec 27, 2019 at 11:47:35AM +0000, Russell King wrote: > Booting 5.4 on LX2160A reveals that KVM is non-functional: > > kvm: Limiting the IPA size due to kernel Virtual Address limit > kvm [1]: IPA Size Limit: 43bits > kvm [1]: IDMAP intersecting with HYP VA, unable to continue > kvm [1]: error initializing Hyp mode: -22 > > Debugging shows: > > kvm [1]: IDMAP page: 81a26000 > kvm [1]: HYP VA range: 0:22ffffffff > > as RAM is located at: > > 80000000-fbdfffff : System RAM > 2080000000-237fffffff : System RAM > > Comparing this with the same kernel on Armada 8040 shows: > > kvm: Limiting the IPA size due to kernel Virtual Address limit > kvm [1]: IPA Size Limit: 43bits > kvm [1]: IDMAP page: 2a26000 > kvm [1]: HYP VA range: 4800000000:493fffffff > ... > kvm [1]: Hyp mode initialized successfully > > which indicates that hyp_va_msb is set, and is always set to the > opposite value of the idmap page to avoid the overlap. This does not > happen with the LX2160A. > > Further debugging shows vabits_actual = 39, kva_msb = 38 on LX2160A and > kva_msb = 33 on Armada 8040. Looking at the bit layout of the HYP VA, > there is still one bit available for hyp_va_msb. Set this bit > appropriately. This allows kvm to be functional on the LX2160A, but > without any HYP VA randomisation: > > kvm: Limiting the IPA size due to kernel Virtual Address limit > kvm [1]: IPA Size Limit: 43bits > kvm [1]: IDMAP page: 81a24000 > kvm [1]: HYP VA range: 4000000000:62ffffffff > ... > kvm [1]: Hyp mode initialized successfully > > Signed-off-by: Russell King > --- I assume it's not possible for kva_msb >= vabits_actual ? > arch/arm64/kvm/va_layout.c | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c > index 2cf7d4b606c3..83f8b3f51cf4 100644 > --- a/arch/arm64/kvm/va_layout.c > +++ b/arch/arm64/kvm/va_layout.c > @@ -22,6 +22,17 @@ static u8 tag_lsb; > static u64 tag_val; > static u64 va_mask; > > +/* > + * We want to generate a hyp VA with the following format: > + * > + * 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0 > + * --------------------------------------------------------- > + * | 0000000 | hyp_va_msb | random tag | kern linear VA | > + * > + * which does not conflict with the idmap regions. This means that hyp_va_msb > + * must always be present. Luckily, when kva_msb == (vabits_actual - 1) we > + * still have one bit for this, but no bits for the random tag. > + */ > static void compute_layout(void) > { > phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start); > @@ -39,19 +50,16 @@ static void compute_layout(void) > /* > * No space in the address, let's compute the mask so > * that it covers (vabits_actual - 1) bits, and the region > - * bit. The tag stays set to zero. > + * bit. > */ > - va_mask = BIT(vabits_actual - 1) - 1; > - va_mask |= hyp_va_msb; > + tag_lsb = kva_msb; > + va_mask = BIT(vabits_actual - 1) - 1; > + tag_val = hyp_va_msb >> tag_lsb; > } else { > /* > * We do have some free bits to insert a random tag. > * Hyp VAs are now created from kernel linear map VAs > * using the following formula (with V == vabits_actual): > - * > - * 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0 > - * --------------------------------------------------------- > - * | 0000000 | hyp_va_msb | random tag | kern linear VA | > */ > tag_lsb = kva_msb; > va_mask = GENMASK_ULL(tag_lsb - 1, 0); > -- > 2.20.1 > > -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel