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Tsirkin" To: Jonathan Cameron Cc: linuxarm@huawei.com, qemu-devel@nongnu.org, linux-cxl@vger.kernel.org, Michael Tokarev , Fan Ni , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [PATCH v4 2/4] hw/cxl: Use switch statements for read and write of cachemem registers Message-ID: <20231019052242-mutt-send-email-mst@kernel.org> References: <20231012140514.3697-1-Jonathan.Cameron@huawei.com> <20231012140514.3697-3-Jonathan.Cameron@huawei.com> <20231018103907-mutt-send-email-mst@kernel.org> <20231018172239.00005f3d@Huawei.com> <20231018173142.00003739@Huawei.com> <20231019100547.00003eef@huawei.com> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20231019100547.00003eef@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Oct 19, 2023 at 10:09:24AM +0100, Jonathan Cameron wrote: > On Wed, 18 Oct 2023 17:31:42 +0100 > Jonathan Cameron wrote: > > > On Wed, 18 Oct 2023 17:22:39 +0100 > > Jonathan Cameron wrote: > > > > > On Wed, 18 Oct 2023 10:40:45 -0400 > > > "Michael S. Tsirkin" wrote: > > > > > > > On Thu, Oct 12, 2023 at 03:05:12PM +0100, Jonathan Cameron wrote: > > > > > Establishing that only register accesses of size 4 and 8 can occur > > > > > using these functions requires looking at their callers. Make it > > > > > easier to see that by using switch statements. > > > > > Assertions are used to enforce that the register storage is of the > > > > > matching size, allowing fixed values to be used for divisors of > > > > > the array indices. > > > > > > > > > > Suggested-by: Michael Tokarev > > > > > Signed-off-by: Jonathan Cameron > > > > > Reviewed-by: Fan Ni > > > > > > > > Fails with clang: > > > > > > > > ../hw/cxl/cxl-component-utils.c:130:9: error: expected expression > > > > QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_regs_write_mask) != 4); > > > > ^ > > > > ../include/qemu/compiler.h:76:30: note: expanded from macro 'QEMU_BUILD_BUG_ON' > > > > #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x) > > > > ^ > > > > ../include/qemu/compiler.h:74:36: note: expanded from macro 'QEMU_BUILD_BUG_MSG' > > > > #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg) > > > > ^ > > > > 1 error generated. > > > > > > > > See e.g. > > > > > > > > https://gitlab.com/mstredhat/qemu/-/jobs/5320879531 > > > > > > Thanks. Will see if I can figure out what is going wrong. > > > This code seems cursed. I need to figure out a way to run the CI again. > > > Ran into credit problems I couldn't solve last time I tried. > > > > > > In meantime I can replicate this locally but not immediately obvious to me > > > why it is failing. > > > > Any clang experts around? This seems to be fixed by reducing the scope > > > > case 4: > > { > > QEMU_BUILD_BUG_ON(); > > } > > I have no idea why though... > > > > For anyone following along I asked a friendly compiler guy... > > https://github.com/llvm/llvm-project/issues/69572 > > Given that we realistically need to work around this whatever the outcome > I'll add some brackets and send an update. > > thanks, > > Jonathan We don't seem to use QEMU_BUILD_BUG_ON outside of functions - just add brackets inside it? > > > > > > > > Jonathan > > > > > > > > > > > > > > > > > > > > --- > > > > > v4: Use QEMU_BUILD_BUG_ON() instead of static_assert with missing > > > > > error message. > > > > > > > > > > hw/cxl/cxl-component-utils.c | 65 +++++++++++++++++++++++------------- > > > > > 1 file changed, 42 insertions(+), 23 deletions(-) > > > > > > > > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c > > > > > index f3bbf0fd13..d1997a52e6 100644 > > > > > --- a/hw/cxl/cxl-component-utils.c > > > > > +++ b/hw/cxl/cxl-component-utils.c > > > > > @@ -67,16 +67,24 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset, > > > > > CXLComponentState *cxl_cstate = opaque; > > > > > ComponentRegisters *cregs = &cxl_cstate->crb; > > > > > > > > > > - if (size == 8) { > > > > > + switch (size) { > > > > > + case 4: > > > > > + if (cregs->special_ops && cregs->special_ops->read) { > > > > > + return cregs->special_ops->read(cxl_cstate, offset, 4); > > > > > + } else { > > > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4); > > > > > + return cregs->cache_mem_registers[offset / 4]; > > > > > + } > > > > > + case 8: > > > > > qemu_log_mask(LOG_UNIMP, > > > > > "CXL 8 byte cache mem registers not implemented\n"); > > > > > return 0; > > > > > - } > > > > > - > > > > > - if (cregs->special_ops && cregs->special_ops->read) { > > > > > - return cregs->special_ops->read(cxl_cstate, offset, size); > > > > > - } else { > > > > > - return cregs->cache_mem_registers[offset / sizeof(*cregs->cache_mem_registers)]; > > > > > + default: > > > > > + /* > > > > > + * In line with specifiction limitaions on access sizes, this > > > > > + * routine is not called with other sizes. > > > > > + */ > > > > > + g_assert_not_reached(); > > > > > } > > > > > } > > > > > > > > > > @@ -117,25 +125,36 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value, > > > > > ComponentRegisters *cregs = &cxl_cstate->crb; > > > > > uint32_t mask; > > > > > > > > > > - if (size == 8) { > > > > > + switch (size) { > > > > > + case 4: > > > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_regs_write_mask) != 4); > > > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4); > > > > > + mask = cregs->cache_mem_regs_write_mask[offset / 4]; > > > > > + value &= mask; > > > > > + /* RO bits should remain constant. Done by reading existing value */ > > > > > + value |= ~mask & cregs->cache_mem_registers[offset / 4]; > > > > > + if (cregs->special_ops && cregs->special_ops->write) { > > > > > + cregs->special_ops->write(cxl_cstate, offset, value, size); > > > > > + return; > > > > > + } > > > > > + > > > > > + if (offset >= A_CXL_HDM_DECODER_CAPABILITY && > > > > > + offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) { > > > > > + dumb_hdm_handler(cxl_cstate, offset, value); > > > > > + } else { > > > > > + cregs->cache_mem_registers[offset / 4] = value; > > > > > + } > > > > > + return; > > > > > + case 8: > > > > > qemu_log_mask(LOG_UNIMP, > > > > > "CXL 8 byte cache mem registers not implemented\n"); > > > > > return; > > > > > - } > > > > > - mask = cregs->cache_mem_regs_write_mask[offset / sizeof(*cregs->cache_mem_regs_write_mask)]; > > > > > - value &= mask; > > > > > - /* RO bits should remain constant. Done by reading existing value */ > > > > > - value |= ~mask & cregs->cache_mem_registers[offset / sizeof(*cregs->cache_mem_registers)]; > > > > > - if (cregs->special_ops && cregs->special_ops->write) { > > > > > - cregs->special_ops->write(cxl_cstate, offset, value, size); > > > > > - return; > > > > > - } > > > > > - > > > > > - if (offset >= A_CXL_HDM_DECODER_CAPABILITY && > > > > > - offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) { > > > > > - dumb_hdm_handler(cxl_cstate, offset, value); > > > > > - } else { > > > > > - cregs->cache_mem_registers[offset / sizeof(*cregs->cache_mem_registers)] = value; > > > > > + default: > > > > > + /* > > > > > + * In line with specifiction limitaions on access sizes, this > > > > > + * routine is not called with other sizes. > > > > > + */ > > > > > + g_assert_not_reached(); > > > > > } > > > > > } > > > > > > > > > > -- > > > > > 2.39.2 > > > > > > > > > > > > > > > > >