From: Ricardo Koller <email@example.com> To: Marc Zyngier <firstname.lastname@example.org> Cc: Zenghui Yu <email@example.com>, Auger Eric <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH v2 4/5] KVM: selftests: Add exception handling support for aarch64 Date: Wed, 12 May 2021 14:39:16 -0700 [thread overview] Message-ID: <YJxLBFBgM29hjtYN@google.com> (raw) In-Reply-To: <firstname.lastname@example.org> On Wed, May 12, 2021 at 05:18:42PM +0100, Marc Zyngier wrote: > On 2021-05-12 17:03, Ricardo Koller wrote: > > On Wed, May 12, 2021 at 02:43:28PM +0100, Marc Zyngier wrote: > > > On 2021-05-12 13:59, Zenghui Yu wrote: > > > > Hi Eric, > > > > > > > > On 2021/5/6 20:30, Auger Eric wrote: > > > > > running the test on 5.12 I get > > > > > > > > > > ==== Test Assertion Failure ==== > > > > > aarch64/debug-exceptions.c:232: false > > > > > pid=6477 tid=6477 errno=4 - Interrupted system call > > > > > 1 0x000000000040147b: main at debug-exceptions.c:230 > > > > > 2 0x000003ff8aa60de3: ?? ??:0 > > > > > 3 0x0000000000401517: _start at :? > > > > > Failed guest assert: hw_bp_addr == PC(hw_bp) at > > > > > aarch64/debug-exceptions.c:105 > > > > > values: 0, 0x401794 > > > > > > > > FYI I can also reproduce it on my VHE box. And Drew's suggestion [*] > > > > seemed to work for me. Is the ISB a requirement of architecture? > > > > > > Very much so. Given that there is no context synchronisation (such as > > > ERET or an interrupt) in this code, the CPU is perfectly allowed to > > > delay the system register effect as long as it can. > > > > > > M. > > > -- > > > Jazz is not dead. It just smells funny... > > > > Thank you very much Eric, Zenghui, Marc, and Andrew (for the ISB > > suggestion)! > > > > As per Zenghui test, will send a V3 that includes the missing ISBs. > > Hopefully that will fix the issue for Eric as well. It's very > > interesting that the CPU seems to _always_ reorder those instructions. > > I suspect that because hitting the debug registers can be a costly > operation (it mobilises a lot of resources in the CPU), there is > a strong incentive to let it slide until there is an actual mandate > to commit the resource. > > It also means that SW can issue a bunch of these without too much > overhead, and only pay the cost *once*. > > Your N1 CPU seems to be less aggressive on this. Implement choice, > I'd say (it probably is more aggressive than TX2 on other things). > Also, QEMU will almost always hide these problems, due to the nature > of TCG. > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny... Thank you, this is very informative.
next prev parent reply other threads:[~2021-05-12 22:59 UTC|newest] Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-30 23:24 [PATCH v2 0/5] KVM: selftests: arm64 exception handling and debug test Ricardo Koller 2021-04-30 23:24 ` [PATCH v2 1/5] KVM: selftests: Rename vm_handle_exception Ricardo Koller 2021-05-03 11:02 ` Andrew Jones 2021-05-06 12:27 ` Auger Eric 2021-04-30 23:24 ` [PATCH v2 2/5] KVM: selftests: Introduce UCALL_UNHANDLED for unhandled vector reporting Ricardo Koller 2021-05-03 11:09 ` Andrew Jones 2021-05-06 12:27 ` Auger Eric 2021-04-30 23:24 ` [PATCH v2 3/5] KVM: selftests: Move GUEST_ASSERT_EQ to utils header Ricardo Koller 2021-05-03 11:31 ` Andrew Jones 2021-04-30 23:24 ` [PATCH v2 4/5] KVM: selftests: Add exception handling support for aarch64 Ricardo Koller 2021-05-03 10:32 ` Marc Zyngier 2021-05-03 19:12 ` Ricardo Koller 2021-05-06 12:30 ` Auger Eric 2021-05-06 19:14 ` Ricardo Koller 2021-05-07 14:08 ` Auger Eric 2021-05-07 17:54 ` Ricardo Koller 2021-05-12 7:27 ` Ricardo Koller 2021-05-12 8:19 ` Auger Eric 2021-05-12 8:33 ` Marc Zyngier 2021-05-12 8:52 ` Auger Eric 2021-05-12 16:06 ` Ricardo Koller 2021-05-12 12:59 ` Zenghui Yu 2021-05-12 13:43 ` Marc Zyngier 2021-05-12 16:03 ` Ricardo Koller 2021-05-12 16:18 ` Marc Zyngier 2021-05-12 21:39 ` Ricardo Koller [this message] 2021-05-07 14:31 ` Marc Zyngier 2021-05-07 18:02 ` Ricardo Koller 2021-05-03 12:39 ` Andrew Jones 2021-04-30 23:24 ` [PATCH v2 5/5] KVM: selftests: Add aarch64/debug-exceptions test Ricardo Koller 2021-05-03 12:49 ` Andrew Jones 2021-05-24 12:14 ` [PATCH v2 0/5] KVM: selftests: arm64 exception handling and debug test Paolo Bonzini 2021-05-24 12:59 ` Marc Zyngier
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