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Mon, 14 Apr 2025 01:52:05 -0700 (PDT) Message-ID: <2bc5ae09-34b9-48e2-840a-2d42c1138e38@suse.com> Date: Mon, 14 Apr 2025 10:52:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] xen/io: provide helpers for multi size MMIO accesses To: Julien Grall Cc: Andrew Cooper , Anthony PERARD , Michal Orzel , Stefano Stabellini , xen-devel@lists.xenproject.org, Roger Pau Monne References: <20250411105411.22334-1-roger.pau@citrix.com> <20250411105411.22334-3-roger.pau@citrix.com> <28db4a69-ea60-4c4d-a6e8-0dcc548a9e75@xen.org> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <28db4a69-ea60-4c4d-a6e8-0dcc548a9e75@xen.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 14.04.2025 09:49, Julien Grall wrote: > On 14/04/2025 15:07, Jan Beulich wrote: >> On 11.04.2025 12:54, Roger Pau Monne wrote: >>> Several handlers have the same necessity of reading from an MMIO region >>> using 1, 2, 4 or 8 bytes accesses.  So far this has been open-coded in the >>> function itself.  Instead provide a new handler that encapsulates the >>> accesses. >>> >>> Since the added helpers are not architecture specific, introduce a new >>> generic io.h header. >> >> Except that ... >> >>> --- /dev/null >>> +++ b/xen/include/xen/io.h >>> @@ -0,0 +1,63 @@ >>> +/* SPDX-License-Identifier: GPL-2.0-only */ >>> +/* >>> + * Generic helpers for doing MMIO accesses. >>> + * >>> + * Copyright (c) 2025 Cloud Software Group >>> + */ >>> +#ifndef XEN_IO_H >>> +#define XEN_IO_H >>> + >>> +#include >>> + >>> +#include >>> + >>> +static inline uint64_t read_mmio(const volatile void __iomem *mem, >>> +                                 unsigned int size) >>> +{ >>> +    switch ( size ) >>> +    { >>> +    case 1: >>> +        return readb(mem); >>> + >>> +    case 2: >>> +        return readw(mem); >>> + >>> +    case 4: >>> +        return readl(mem); >>> + >>> +    case 8: >>> +        return readq(mem); >> >> ... this and ... >> >>> +    } >>> + >>> +    ASSERT_UNREACHABLE(); >>> +    return ~0UL; >>> +} >>> + >>> +static inline void write_mmio(volatile void __iomem *mem, uint64_t data, >>> +                              unsigned int size) >>> +{ >>> +    switch ( size ) >>> +    { >>> +    case 1: >>> +        writeb(data, mem); >>> +        break; >>> + >>> +    case 2: >>> +        writew(data, mem); >>> +        break; >>> + >>> +    case 4: >>> +        writel(data, mem); >>> +        break; >>> + >>> +    case 8: >>> +        writeq(data, mem); >>> +        break; >> >> ... this may (generally will) not work on 32-bit architectures. Add >> CONFIG_64BIT conditionals? At which point return type / last parameter >> type could move from uint64_t to unsigned long. > > Technically arm32 bit supports 64-bit write because we mandate LPAE. I see this is used by the vPCI code. Are we expecting to have any 64-bit access? vPCI is, I think, supposed to not see 64-bit accesses (to config space). However, vMSI-X already may see such. Jan